Moto Bug is the first enemy you ever encounter in Sonic. Is the series' Goomba, in other words, and there's one in Sonic Mania named after a member of the Sonic hacking community who died a few years back.
Named Jimmy after the late Polygon Jim, it appears in the Lava Reef Zone as part of the Heavy Rider boss fight, which the Sonic the Hedgehog blog called attention to in a post earlier today. As an enhanced Egg-Robo, Heavy Rider uses Jimmy as a mount while battling Sonic in the stage's second act. Jimmy isn't an ordinary Moto Bug, however. Unlike the normal kind which have been a mainstay of the series ever since Sonic 1, Jimmy jumps.
It's part of a call back to one of Polygon Jim's better known contributions to the Sonic hacking community. Motobug the Badnik in Sonic the Hedgehog takes the original game and reskins it. Instead of playing as Sonic you play as a Moto Bug, with spare parts instead of extra lives and the sign at the end of levels depicting the lady-bug looking robot instead of a blue hedgehog. Most importantly, the Moto Bug from Polygon Jim's hacked ROM can jump just like Sonic, shooting out its single wheel Inspector Gadget-style to launch it into the air.
That's why in addition to being named Jimmy, the Moto Bug from Sonic Mania also allows Heavy Rider to hop around the stage. It's just another example of the fandom-fuelled passion and attention to detail that went into making the game. Far from just being a remixed nostalgia trap or "remember when?" highlight reel, PagodaWest turned Sonic Mania into a radical tribute to the series' history and the fans who have kept it alive.
Polygon Jim died in a car crash back in 2013, so giving his work a posthumous nod is a nice way of honouring the contributions that have helped make Sonic more than just the sum of its parts.