Cuphead is fantastic! Here's some ideas for bosses:
Babyface Vito: A big, hulking mobster with a literal baby face. He uses a massive tommy gun, and eventually becomes different baby toys. Rocking horse, maybe a mobile, that sorta thing!
Baron Elephante Gunn: The quintessential British explorer. He and his expedition crew battle Cuphead in a jungle teeming with mischievous monkeys and poisonous snakes!
Percy Scription: Inspired by the obscure but mildly horrifying short Bottles, Percy is an animate bottle of some strange medicine. Throughout the fight, which takes place on a doctor’s desk, Percy uses the fluid inside him and summons other flasks to aid him!
Lexi Kahn: A huge bookworm who fights Cuphead by bringing her favorite stories to life! Expect to be besieged by works like Alice in Wonderland, The Wizard of Oz, and more!
Old Man Time: A classic: a living, time-manipulating Grandfather Clock! He’d have some neat tricks involving bringing things from the past to the present!
Mr. Acme: A literal fat cat businessman who fights with money, cigars, and his famous ACME Brand products! Expect portable holes, anvils, all the greats!
but then you already fucking know why the cats are fat. they literally don't get any exercise at all. they live inside a prison. oh my god? americans....
Uh, don’t “Americans” me, please, unless you’re going to blame us for having roads and cars, because the average lifespan of an outdoor cat is under five years old, and Rosie will be eleven next month. I would rather see her fat than crushed, thank you very fucking much. And I would gladly play with her more to make sure she gets exercise, but I have this little problem of having a serious chronic illness that makes it very difficult to simply bathe myself, much less exercise my cats. My cats are happy and well-loved. Mind your own business.