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).