Things got confusing when animation studios started anthropomorphizing animals, though. "Her blouse had to be buttoned up with no cleavage."
"When the production code was first enforced in 1934, Betty Boop's dress had to suddenly become longer," Cohen tells SYFY WIRE. Human characters, even when sporting exaggerated features, were suddenly held to the same standards as live-action actors. Animation historian and San Francisco State media professor Karl Cohen says that early production codes responded to cartoon nudity in an inconsistent manner. Most cartoon characters are unaware that they're naked, unless a designer puts them into a costume.
It helps to turn the question around and look at it another way: the act of putting an item of clothing on a cartoon animal actually introduces the subject of nudity. So how are these costuming decisions made in the first place? It's now the norm for anthropomorphized characters to wear a bit more clothing than their predecessors (think of Paddington's smart little toggle coat or SpongeBob's suspenders and dress shirt), but nudity is still somewhat prevalent, and companies tend to leave the original figures in their various states of undress. If an animator pitched a human character for a children's show who dressed in this manner, they'd probably be arrested, or at least put on some kind of industry watch list. Mickey Mouse wears a pair of pants and gloves, and Bugs Bunny just wears gloves. Sonic the Hedgehog sports only sneakers, socks, and white gloves as he chases rings. Winnie the Pooh cavorts around the Hundred Acre Wood wearing naught but a T-shirt, exposing his round, golden bottom to the elements. Animated animal protagonists in children's cartoons aren't usually naked, but they're rarely fully clothed.