Yet more AU nonsense from Theorychat.
The big fella is Petboi, and the little gremlin on his shoulder is Jarboi.
Petboi is an Eclipse from an AU where after being defeated and his star confiscated, Moon and Lunar thought it'd be hilarious to punish Eclipse by making him their pet instead of killing him. This turns out to be somewhat of a mistake, because although they disabled his ability to speak, made it so he can't really use his hands, and gave him a tail, he chooses to go around on all fours, and still causes as much trouble as possible.
At some point everyone gets tired of him actually taking his punishment to heart and acting the part of a spoiled animal, so they re-enable his voice and insist on treating him like a normal family member. But being the stubborn thing he is, Eclipse continues the game. "You wanted a pet? You got one." He refuses to use his voice beyond growling, hissing, and other assorted animalistic noises, for the pure entertainment factor and watching them get frustrated with him. His behavior is a mix of dog and cat, and he's learned to enjoy stealing Lunar's beanbags for a bed after he ripped up the giant dog bed they got for him when he first came home with Moon and Lunar. He started enjoying being the pet at some indetermined point, enjoying the fact that nothing is expected of him and he can basically just do whatever and have all his needs met. The rest of the daycare family just gave up trying to force him to act normally again when it was clear he wasn't going to even try, so they just treat him the way he acts. Doesn't stop him from being miffed when Sun asks if "anyone fed the dog today" though.
And yes, bellyrubs make his legs go wild. He loves it, but you didn't hear that from me.
Jarboi is from an AU by @starays13 Where Eclipse's punishment was being shrunk to roughly 5 inches tall. The poor tiny boi is full of rage, but can't do anything about anything. For the first few months they kept him in a jar to keep him in one place and not get lost. He has to be plugged in by someone else like a cell phone to charge, and is basically a fun living toy for supervised play with the kids during daycare operating hours.
When there's cross AU visits between multiple Eclipses, Petboi and Jarboi are either causing trouble together or tormenting eachother. Jarboi has gotten more than one tongue bath from Petboi, but it doesn't stop him from cussing out the other version of himself.