Sonic Mania contains a lovely tribute to a Sonic hacker who died tragically in 2013.
Polygon Jim, real name Cody Lawrence, was a member of the Sonic hacking community who died in a car crash aged just 21. He was known for the Motobug the Badnik hack in the first Sonic the Hedgehog. In this hack the main character Sonic the Hedgehog is replaced by Motobug, one of Dr. Robotnik's badniks and the first enemy you ever encounter in Sonic. You can jump by extending its wheel.
According to a post on the Sonic the Hedgehog blog, the developers of Sonic Mania placed Jimmy, named after the late Polygon Jim, in the Lava Reef Zone as part of the Heavy Rider fight. Just like in the Motobug hack, Jimmy jumps. Here's how it looks:
It's a lovely tribute to a prominent Sonic hacker and perfectly appropriate for Sonic Mania, a game which owes much of its success to the development skills of hackers and modders. For more on Polygon Jim, head over to this obituary on Sonic Retro.