Uncle Chuck--The Legend

In early canon, "Uncle Chuck" was a very important character. A good inventor opposed to the malicious Dr. Robotnik, early works credit Chuck with inventing the "power shoes" (speed-up shoes) and "power rings" (rings). 

Of Sonic's relatives, he's the most reoccurring. The details change, but at its simplest, Chuck was close to Sonic and helped inspire him to take on Dr. Robotnik. 

Sat Am

In one of Sat Am's most emotional moments, Sonic reunites with his robotized Uncle Chuck and tries to use a power ring to save him. Eventually (in Season 2) they are able to restore his personality and Chuck is able to help them. However he remained robotsized on the outside. It was also revealed that "Charles" himself created the Robotsizer--to prolong life--but "Julian" Robotnik took the design for his own dark purpose. 

Underground

Uncle Chuck reappeared in Sonic Underground as a part of Sonic's origins. While his exact relation to Sonic/Aleena is not made clear, it's assumed (via appearance) that they are still related. At some point Sonic met Chuck in his early childhood, and after his adoptive family was robotisized (and his home burned to the ground), Chuck took him in. Chuck taught him to be a freedom fighter, but like his Sat Am counterpart he was robotisized. 

"Grandpa Chuck" of Sonic X

Despite relying more on the games and Sonic Team for background on Sonic X, some elements of Western canon leaked into the anime. One of these elements: Grandpa Chuck (Chuck Thordyke). Chuck is Chris' grandfather, rather than Sonic's uncle, and he's a human. However he shares his intelligence and talent for inventing. Over the series Chuck would grow closer to Tails, becoming a role-model with an almost uncle-like relationship to him.  

Comics

Uncle Chuck was faithfully adapted into the Archie Comics as Sir Charles the Hedgehog, brother of Sonic's father, Jules (and brother-in-law to Bernadette). Later in the series run, he was restored to his Mobian self, defended Sonic and the others as a member of a council, and helped with the Secret Freedom Fighters (featuring the likes of Sally's brother, Elias, and Silver the Hedgehog).  

Following the reboot, Sega created the condition that game characters could not have family members unless they already appeared in the games (such as Cream's mother, Vanilla).  Ian Flynn got creative and brought Charles back with the label "Uncle to Everyone," under the guise that his relationship to Sonic was adoptive (this character was allowed to return because he came from the Sat Am TV show, rather than Penders-written comic characters like Jules and Bernadette). 

Despite this, Sonic was shown to be very close to his "Uncle" and Charles likewise tried to look out for Sonic. Over the course of the Unleashed-adaptation, Charles was also revealed as a friend of Professor Pickle. His role in this series, though, would be his last.  

Uncle Chuck survived a comic reboot, appeared in 2 cartoons, and inspired another character. Many have tried to mimic the emotional bond between Sonic and Chuck, but the character remains one of the closest to Sonic, even visually. It's a shame the character's gone for now, but who knows? Perhaps he'll inspire someone else...

Sonic Forces References

The game celebrated 25 years and also had some callbacks:


Words narrate the events, similar to the date/location given in SA2 cutscenes.

Eggman takes over the world while Sonic is away. This happened in Sonic the Comic and later in Sonic Chronicles: The Dark Brotherhood.

Eggman also took over in several other continues, but while Sonic was young, not missing. 

Knuckles leads the Resistance: a "rag-tag" team of fighters to "take back the planet." This group helps rescue Sonic after his 6-month capture.

This idea may have been inspired by:

• The (Knothole) Freedom Fighters, generally led by Sally Acorn in Sat Am and the Archie Comics. 
• The Freedom Fighters, founded by Sonic in Sonic the Comic. 
• The Resistance, the "underground" movement against Robotnik in Sonic Underground. 
• Team Hero, Sonic and his close friends who often fight Eggman in the games. 
• The Resistance, a group of humans that fought the Meterex in Sonic X. 

Green Hill, Chemical Plant, and the Death Egg all appear again.

This is the second anniversary game where Sonic fights Metal Sonic. 

Sonic says to Classic, "it's been generations since I've seen you," alluding to Sonic Generations.

Sonic's box artwork is similar to his art for Sonic Rivals 2.

Many trophy/achievement names are based on games/phrases.

The Avatar's clothing can reflect other characters (such as a Tails shirt with Knuckles' shoes or a chao backpack and Amy's boots).

Omega is broken down/out of commission for most of the game. Something similar happened in 06 as well as Sonic Chronicles.

Infinite refers to Sonic as a rat. This was something the Erazor Djinn often said in Sonic and the Secret Rings.

Shadow kicks Infinite in nearly the same way he kicks Silver in the head in 06.

The Shadow "replicas" mainly serve the same purpose as "Shadow Androids."

Episode Shadow has remixes from Sonic Adventure 2 and Shadow the Hedgehog. A part of "All Hail Shadow" can also be heard when he appears in the main story.

Update: How could I forget?! The US theme for Metal Sonic/Stardust Speedway Bad Future was also remixed! Sonic CD!

Rouge mentions an "intelligence division." This may implicate GUN.

Rouge tells Shadow "do it to it," which was a common phrase in the early cartoons.

Rouge indirectly mentions chilidogs.

Rouge also called Eggman "Rotton ol' Eggman." Even though she used to call him "doctor," I swear she's called him something like that before...  

Sonic Generations: Current Continuity

CURRENT

Characters

• Sonic
• Sonic mentions Yacker as an alien and that he saved them. 
• Orbot and Cubot
• Return via cameo from Sonic Colors.
• Time Eater
• Resembles the Void-wisp. 

Levels

• Planet Wisp

Returning elements

• Red Star Rings (First Appearance: Sonic Colors)
• 3D Super Sonic in stages (First Appearance: Sonic Colors)

Music

• Standard (Remixes)
• Planet Wisp
• Unlockables
• Reach for the Stars
• Tropical Resort
• Sweet Mountain
• Free
• Splash Hill

Other Similarities

• The Egg Dragoon is fought in a similar setting to the final boss in Sonic Colors. 

Sonic Generations: Modern Allusions

MODERN

Characters

• Sonic
• Sonic goes boarding in City Escape. He goes boarding in several Modren games, especially in the Riders series. 
• Sonic mentions Sharah and the Storybook series indirectly as "genies & magic books."
• Sonic's idle animations are similar to the ones from Sonic Unleashed. 
• Sonic's favorite meal--chilidogs--appear again. The were established as such in the games in Sonic Unleashed. 
• Tails
• Tails does his 06 animation with his tails. 
• Knuckles
• Knuckles' second animation is also from 06. 
• Blaze
• Blaze can be seen talking to Cream. She made friends with the rabbit in Sonic Rush.
• Similar yet different music plays for Blaze in Sonic Rush, just as similar-different music plays for Classic Sonic.  
• Blaze has a move similar to one from the Rush series. 
• Blaze refers to her home dimension. 
• Blaze refers to being in Crisis City. She also uses the phrase "again" which was one of her sayings in Sonic Rush.  
• Blaze helps Sonic with the flames in Crisis City, a reference to her immunity in Sky Babylon. This move may also be inspired from the planned Blaze/Silver move in Sonic 06. 
• Shadow
• Shadow looks around and crosses his arms; his idle animation from 06. 
• Shadow's theme "All Hail Shadow" returns. 
• Rouge
• Rouge distracts the enemies in her help/challenge act by blowing them kisses. This was one of her basic attack moves in Sonic Riders. She would also "distract" in Sonic Chronicles: the Dark Brotherhood.  
• Her heart-bombs from 06 reappear. She's used different bombs throughout the games.
• One idle animation of Rouge is tossing her "hair" like in 06.  
• Rouge's nickname for Sonic, "Big Blue," comes from Sonic Chronicles: the Dark Brotherhood.  
• Silver
• Silver messes with his gloves--and idle animation from 06. 
• He uses his catchphrases such as "Take this" and "Give up!" (but not his famous line, "IT'S NO USE.").
• Eggman
• Sonic must fight two "eggmans," just as he had to fight two "eggmans" in the Rush series (the other was Eggman Nega). 
• "Bombs away" and "Time for a change of pace" return from Sonic Unleashed.  
• Time Eater
• The Time Eater is similar to Solaris (Sonic 06), both in setting and concept. It's dark appearance is also similar to the Dark Queen (Sonic and the Black Knight) and the setting is similar to Exception (Sonic Rush). 
• The Time Eater's final attack is similar to Iblis (phase 3) attack against Silver as well as Alf Layla Wa-layla's attack against Darkspine Sonic in Sonic and the Secret Rings and Perfect Dark Gaia's final attack in Sonic Unleashed. 
• Latin lyrics are heard in Solaris Phase 1, and Latin words are also spoken for the Time Eater boss fight. 

Levels

• Crisis City
• Spagonia/Roof Top Run
• Eggman Land (boss)

Returning Elements

• Boost (First appearance: Sonic Rush)
• Super combined attack (First appearance: Sonic Rush)
• Multi-dimensional boss fight (First appearance: Sonic Rush)
• Starting Boost (First appearance: Sonic and the Secret Rings)
• Time Break (First appearance: Sonic and the Secret Rings)
• Skill System (First appearance: Sonic and the Secret Rings)
• Balloon Cluster (First appearance: Sonic Unleashed)
• Skydiving (First appearance (as Sonic): Sonic Unleashed)
• Wall Jump (First appearance (as Sonic, 2-D): Sonic Unleashed)
• Stomp (First appearance: Sonic Unleashed)

Music

• Standard (Remixes)
• Crisis City
• Dreams of Absolution (when standing near Silver)
• Vs Player music from 06
• Roof Top Run
• Egg Dragoon
• Unlockables
• His World 
• Wave Ocean
• Kingdom Valley
• Endless Possiblity
• Windmill Isle (Day)
• Savannah Citadel (Day)
• Right There, Ride On
• A New Venture
• High Flying Groove
• Un-Gravitify
• Quick Trip to Paradise
• Race to Win
• Let the Speed Mend It
• Knight of the Wind

Level Mechanics

• Tricks fill the boost, as in Sonic Rush.
• The spinning tops work similar to some moving items from the Rush series. 
• Classic Sonic grabs a balloon in a Roof Top Run mission, similar to the floating balloon in Sky Babylon. 
• Elements of Crisis City are similar to Chaos Inferno. 
• Elements of Sky Sanctuary are similar to Babylon Garden. 
• A 3D slide appears in Chemical Plant, just like the one in Aquatic Capitol.  
• The lava spewing out in Crisis City was originally in Flame Core. 
• The giant turtles from Tropical Jungle appear in Seaside Hill (though they are also like the smaller ones of Dry Lagoon). 
• Parts of Chemical Plant resemble Eggman Land. 
• Roads and elements of Speed Highway are a lot like Empire City's Sky Scraper Scamper. This also includes name-cameos on street signs. 
• The design of the saws come from levels such as Sky Scraper Scamper and Eggmanland from Sonic Unleashed. 
• The swinging metal obstacle comes from Jungle Joyride. 

Other Similarities

• The rival races are similar in gameplay to the Rivals series. 
• Cream's race to find the Chao is similar to the Capture the Chao levels in Sonic Rivals 2 as well as a mission in Sonic Unleashed. 
• Many rivals in Sonic Rivals are rivals in this game. 
• Metal Sonic just makes sound effects, like in the Rivals series. 
• The rival races are sort-of similar to the Johnny races of Sonic Rush Adventure. 
• The Crisis City "Red Star Ring Shortcut" (Act 1, Ring # 2) is a reference to the shortcut in Silver's level as well as the location of the first Chaos Emerald in End of the World.   
• The skill equip is like the Gem/shoes from 06. 
• Upgrading weapons in Sonic and the black Knight is also similar to the skill system. 
• There is a small flame in front of the entrance, which must light the entrance. Darkness is also shown as a black/purple color. These two combined may be a reference to Iblis/Mephiles, or to Solaris.  
• The entrance to the Time Eater boss looks like an Eye of Solaris from End of the World and the Solaris fight. 
• In Sonic and the Black Knight, the Medal of Sonic is "What 'm Made of" and the Medal of Lancelot (Shadow) is "All Hail Shadow"--these play for their respective attacks during the Final Rush (Shadow) Rival Battle. 
• The Skill Shop has Wentos' chao puppets and Chaos Cola (from Sonic Unleashed). 
• The world flags from Unleashed are all visible in Roof Top Run.  

Sonic Generations: Transitional Recollections

TRANSITIONAL

Characters

• Sonic
• Sonic does poses similar to art of the early 2000s. 
• Sonic gets help in the challenge acts, sometimes in a way similar to Sonic Advance 3. 
• Classic Sonic's Treasure Scanner is similar to Rouge's Treasure Scope or Knuckles' Sunglasses. 
• Sonic goes boarding in City Escape...once again. 
• Amy
• Amy's hammer moves are similar to those from Sonic Adventure/Sonic Battle/ Sonic Heroes. 
• Amy's move with Sonic from Advance 3 is similar to what she does in a challenge act. 
• Knuckles
• Knuckles' treasure hunter status is recalled. 
• Shadow
• Shadow crosses paths with Sonic like he does in Sonic Adventure 2: Battle's opening.
• Shadow's Chaos Spear move returns. 
• In the Shadow rival battle, Sonic races forward--getting 10 rings--before the level actually starts. This is a reference to Shadow having 10 rings at the start of each battle (in Shadow the Hedgehog).
• Shadow is can be the 3rd or 4th Chaos Emerald to get. In his own game he searches for "that DAMN 4th CHAOS EMERALD."
• Shadow's Chaos Control usage in Shadow the Hedgehog boss battles slowed time, similar to Time Break. Team Dark's move in Sonic Heroes also resembled this (though it froze time).   
• When fighting Shadow, the character's music may change when attacking, like it does when using Chaos powers in Shadow the Hedgehog. The song itself is a version of "All Hail Shadow," which debuted in Shadow the Hedgehog. 
• Vector
• Vector's detective skills are referenced. 
• Cream
• Cream tries to find chao before Sonic. This is inspired from "Find the Lost Chao" of Sonic Adventure 2 and to Cream's search for Chocola in Sonic Heroes. 
• Eggman
• "Prepare to be skewer-ed" is said in Egg Dragoon--a reference to Pawn Fever (Shadow the Hedgehog). 
• Chaos
• The different Perfect Chaos design is what the monster was supposed to look like in Sonic Adventure (but didn't due to the technology of the time).  
• Omachao
• Returns to give hints like his debut in Sonic Adventure 2.

Levels

• Speed Highway
• Station Square (boss)
• City Escape
• Final Rush (rival)
• Seaside Hill

Returning Elements

• Orca (First appeared: Sonic Adventure)
• Ring the Bell (First appeared: Sonic Adventure)
• Chao in Space (First appeared: Sonic Adventure)
• Helicopter (First appeared: Sonic Adventure)
• "Buy" Stuff (First appeared: Sonic Adventure DX: Director's Cut)
• Super Fight--Tag out/in (First appeared: Sonic Adventure 2)
• Floating Level Debris in Final Boss (First appeared: Sonic Heroes)

Music

• Standard (Remixes)
• The Settings is Heroes' Character Select music. 
• Challenge Act "Mission 3" was remixed music from Sonic Battle. 
• Speed Highway
• Vs Perfect Chaos
• City Escape
• Throw It All Away (when standing near Shadow)
• Final Rush
• What I'm Made Of (Sonic's theme in Vs Shadow)
• Seaside Hill
• E.G.G.M.A.N. (Outside of boss area)
• Unlockables
• Open Your Heart
• It Doesn't Matter
• Metal Harbor
• Live and Learn
• Green Forest
• Sonic Heroes
• Sonic Heroes Special Stage
• What I'm Made Of
• Neo Green Hill
• Leaf Forest
• Route 99
• I am...All of Me

Level Mechanics

• The Homing Attack is prominent in Modern stages. This began to become standard after Sonic Adventure.
• There are three paths in Seaside Hill, just as in the original (as there were 3 characters).   
• In Seaside Hill, the Egg Pawns wield their Egg Guns, as in Sonic Heroes. However the weapons look more like their Shadow the Hedgehog versions.  

Other Similarities

• The limit on the skills is similar to Ermel's customization limit in Sonic Battle. 
• Neo Metal Sonic using Chaos Control to stop time is similar to a move by the Time Eater. 

Sonic Generations: Classic Callbacks

CLASSIC

Characters

• Sonic
• Classic Sonic's idle animations such as tapping his foot, crossing his arms, and laying down all originated in the classic games. 
• Sonic 1 started the foot-tappping, Sonic 2 started the laid down one, Sonic 3 had the "shooter" pose, and Sonic 3D blast had the arms crossed. 
• He'll also pose in the same way as many of the 90s art, such as with a pointer finger or in an almost running position. 
• Tails
• Tails' animation likewise comes from Sonic 2.   
• Metal Sonic
• Sonic has to fight a metal version of himself, as he does in many classic games. 
• Amy
• Amy was saved by Sonic...once again. 
• Knuckles
• Knuckles likes grapes (according to the old manual).
• Knuckles was the 3rd character to appear. 
• Knuckles races Sonic; Knuckles is a long-time rival. 
• Knuckles' first idle animation with his fists is from Sonic and Knuckles and his other playable appearances. 
• Eggman
• He is called "Robotnik" for the first time in about 10 years. 
• He tries to use time travel to his advantage, as he did in Sonic CD. 

Level Appearances

• Green Hill
• Chemical Plant
• Death Egg (boss)
• Stardust Speedway (rival)
• Sky Sanctuary

Returning elements

• Lives (first appeared: Sonic 1)
• Basic Shield (first appeared: Sonic 1)
• Elemental Shields (first appeared: Sonic 3)
• Power Sneakers (first appeared: Sonic 1)
• Invincibility (first appeared: Sonic 1)
• TV Box (Challenge Act/Skills; first appeared: Sonic 1)
• 7 Chaos Emeralds (first appeared: Sonic 2)
• Super Sonic (first appeared: Sonic 2)
• Super Sonic in a final fight (first appeared: Sonic and Knuckles)
• Moving Goal Sign (Challenge Act; first appeared: Sonic 3)
• Homing Attack (first appeared: Sonic 3D blast--as a shield) 
• Drowning (first appeared: Sonic 1)

Music

• Standard (Remixes)
• Super Sonic Racing (theme of Sonic R) plays during some challenge acts.
• Green Hill
• Chemical Plant
• Death Egg (Sonic 2)
• Stardust Speedway Bad Future (JPN)
• Sky Sanctuary
• Sonic 2 2-Player (heard at store)
• Unlockables (some remixed)
• Green Hill Zone
• Marble Zone
• Starlight Zone
• Emerald Hill Zone
• Chemical Plant
• Sonic 2 Specail Stage
• Angel Island
• Hyrdocity
• Marble Garden
• Mushroom Hill
• Flying Battery
• Toxic Caves
• Sonic Boom (US)
• Stardust Speedway Bad Future (US)
• Palm Tree Present (JPN)
• Diamond Dust 
• Super Sonic Racing 

Level Mechanics

• Saws appear like in Scrap Brain Zone
• There is the see-saw element from levels like Star Light Zone
• The Spinning Tops are based on the ones from Marble Garden
• Underwater: 
• Spikes such as in Labyrinth, Hydrocity, Tidal Tempest, etc
• Water current/flow such as in Labyrinth and others
• Slide such as in Labyrinth and others  

Other Similarities

• Green Hill
• The "corkscrew" path is based off the ones in Emerald Hill. 
• Sky Sanctuary
• The spinning tops resemble the UFOs of Marble Zone.
• The insides of Sky Sanctuary resemble Hidden Palace.
• City Escape
• City Escape's crushers are similar to the finale of Sonic 1. 
• Seaside Hill
• There is an angel statue; it is a reference to the Wacky Workbench Easter Egg. 
• Crisis City
• Some of the set-up resembles Marble Zone as well as Laval Reef.
• Sonic runs upward, like he does in Palm Tree Panic. 
• Roof Top Run
• Roof Top Run's moving platforms are similar to the ones in Hill Top Zone. 
• Sonic skateboards in City Escape like he snowboards in Ice Cap.
• The Eggman ship in Roof Top Run resembles the Flying Battery ship. 

Sonic Generation References

There are many references in Sonic Generations that paid respect to the then 20-year anniversary.

General

• Stances similar art to box art and Sonic Channel through out the game
• Characters who do not appear have cameos such as Omega
• Gen uses the ranking system to S-rank, a modern trait. 
• The different poses for ranks originates from Sonic Unleashed. Previously it would just be the same pose and a differing phrase said by the character. 
• Sonic's "running pose" on the cover resembles 06, Rivals, etc
• The player earns "points" instead of rings, something unique. 

Next Up: 90s Nostalgia--the classics. Then Traditional, Modern, and Current.

Chilidogs

Sonic's favorite food is chilidogs. This was a re-occurring case in the Sonic cartoons and comics that even influenced the games. Starting with Sonic Unleashed (2008), the food was officially his favorite and would make subsequent appearances. 

90s

The origin of Sonic's love of Chilidogs began in Adventures of Sonic the Hedgehog, appearing often in the series. Tails was also a fan.

Sonic the Hedgehog ("Sat Am") also incorporated the element into many of it's episodes. The comics followed suit, though they appeared less frequently as the series continued. 

Sonic Underground immediately picked up the idea again when it aired. It wasn't unusual for Sonic to gulp down chiligdogs in large quantities.

2000s

"Pretty Tasty"

Sonic X was the first cartoon to largely ignore the tradition, possibly because it was the first series not by DiC Entertainment or the first not made under "western" cannon. However there was ONE in the episode "How to Catch a Hedgehog" (it was not called so by name, just seen). It was clearly at least a cameo-reference. 

When food became a large part of Sonic Unleashed, Chilidogs were described as Sonic's favorite. Sonic could also earn different versions of dogs by doing missions.

Again they were shown as Sonic's # 1 food in Sonic and the Black Knight.

2010s

Tails gives Sonic one as a gift in Sonic Generations, and it's shown as a popular food item at Sonic's birthday party. Though somewhat referenced in dialogue, Chilidogs kinda' disappeared.

Luckily Sonic Boom carried on the "Chilidog tradition" and used it in the show. However the writers were originally on the fence about whether they should have.

Sonic's Fear

Sonic's Fear of Water

Since Sonic 1's Labyrinth Zone, Sonic's distaste for water turned into a fear.

Sonic hitches a ride off Manic in "Head Games"

Though early canon showed that Sonic disliked water, it was not until Sonic Underground that it completely turned into a fear. Though Sonic "faced his fear" in "The Deepest Fear," his persistent hydrophobia would be a a reoccurring gag through out.

Sonic freaks before realizing he fell in shallow water in "Cracking Knuckles"

Though Sonic X ignored many elements of "western canon," Sonic's fear was shown in the very first episode. Like in Underground, Sonic's fear caused him to act off, perhaps moreso. Sonic sort-of faces his fear in "Cruise Blues," but not before doing everything in his power to try and get away from the situation. This was also a reoccurring gag throughout this series.

Sonic Channel Art

The games never officially addressed whether Sonic had a fear. He's faced many water levels, but it's obvious that he can not swim. Some of the Olympic games have Sonic in a life-vest.

In Razor the Sharks' "Origins"

Again, Sonic was shown weary of water Archie comics, notably in the story arc "Waves of Change." Still, he was portrayed as more comfortable with it compared to previous versions.

Sonic Boom also carried the idea into its show, hinting at it from the start and focusing on it in the episode "I Can Sea Sonic's Fear From Here."

Sonic Racing (in Cartoons)

TSR/"Overdrive" Short

Every Sonic cartoon has managed to make a race-centric episode. Considering that this is Sonic, it makes a lot of sense.

Adventures of Sonic the Hedgehog

"Mobius 5000"
In this episode, Sonic and Tails participate in a race to save an orphanage. This race is done in a car. Also, there more references to the games than normal, featuring several versions of zones and the Special Stage. 

Sonic the Hedgehog "Sat Am"

"Sonic Racer"
Dr. Robotnik lures Sonic into a trap with something he can't resist: a chance to prove he's the fastest. Though the plan is for Sonic to be a distraction, Sally is worried the hedgehog's ego will get him into deep trouble.

Sonic Underground

"Winner Fakes All"
Robotnik's done it again! This time, though, Sonic realizes that participating may not be the best idea and decides to let it go. Unfortunately his siblings know him too well and think he's in the race.

Sonic X

"Fast Friends" (Jp: "Speed Match! Sonic vs Sam")
Sam Speed, Chris' uncle, has had a rivalry with Sonic since he showed up in "Chaos Control Freaks." This need to prove who is faster comes to a climax as he demands a race with the support of the government...and Eggman.

Sonic Boom

"Blue with Envy"
A new character, Swifty the Shrew, starts stealing the spotlight, and than he cons Sonic into a race. But things are not as they seem...

Sonic's Guitar

Sonic was originally planned to be in a band in the Sonic 1 Sound Test, but that idea was scrapped. Still he was only a singer and not playing guitar. That seems to be taken up by the cartoons...

AoStH

Sonic can be seen playing guitar for...the first time?

Sat Am

Sonic's guitar appeared twice--one was in the pilot.

The other was part of a make-shift disguise.

Underground

The guitar became a musical weapon and used throughout the series.

A red version similar to the Sat Am one was in the episode "Beginnings."

As well as a "baby" one.

Sonic X

Sonic never played the guitar...but Prison Island sure looks like one!...and it...didn't in the games...

Sonic Boom

Sonic picked up the guitar again. Red, like some of his past, and it's three-necked like Underground.

Movie

Sonic briefly plays a green guitar.

Madonna

Madonna was Sonic's scrapped girlfriend for the original Sonic the Hedgehog.

AoStH

Breezie, who was initially a love interest for Sonic, wears an outfit similar to Madonna.

A Madonna-like figure can be seen in the episode, "The Mystery of the Missing High-tops"

One of Sonic's disguises also bears a resemblance.

Other Cartoons

A random human female is visible in a Sonic Underground episode. This is very odd because Underground doesn't usually have humans other than Robotnik. Though she is colored different, she does bare some similarities in design. 

Though visually different, the OVA revisits the idea of a human-like love interest for Sonic.

Chris' mom somewhat resembles Madonna.

Games

Madonna may have inspired Amy's modern redesign (red dress, short cropped hair).

The idea of a human love interest would be revisited again in Sonic 06.

Archie

The character was revived as GUN agent "Madonna Garnet," also taking inspiration from Topaz (Sonic X).