Sonic the Hedgehog (character)

Sonic the Hedgehog was the main character in the video game of the same name.

He was a blue hedgehog. (PROSE: Business Unusual)

Ace joked with Dr John Watson that whatever the Rakshassi were worshipping, it wasn't Sonic the Hedgehog. (PROSE: All-Consuming Fire)

Martha Jones once described the Tenth Doctor's hair as "very Sonic the Hedgehog", although the Doctor said he was going for more of a Sid Vicious vibe. (PROSE: Forever Autumn)

Non-valid appearances
Sonic swiped a floating ring out of Gollum's grasp inside a dark cave. (NOTVALID: New Adventures Await!)

Sonic once found himself inside either the First or Second Doctor's TARDIS, where he ran up beside the Twelfth Doctor, who was looking at his blackboard. Upon noticing Sonic, the Doctor whipped out his sonic screwdriver in surprise. (NOTVALID: Sonic the Hedgehog Joins LEGO Dimensions!)

Sonic had apparently heard of the Doctor before meeting him, and was impressed when he erroneously heard that he named the sonic screwdriver after him. (NOTVALID: LEGO Dimensions)