The old television and movie trope imagines a devil and an angel appearing on the opposing shoulders of a character who has a difficult moral decision to make.
Cats, though, operate in a different cosmology than humans and lack the same ethical enforcers. No one is telling your cat to not eat any interesting food that he encounters. The devils are just competing for who can come up with the most vicious option available. Had there been a fourth devil in this episode of Ellen Woodbury’s Pizza Cake Comics, he might have suggested puking on the bed shortly before the humans went to bed.