There are a lot of half-dressed and accessory wearing animal characters because a full outfit has a high chance of obscuring the character's species, especially if they are also wearing shoes or socks. Often, the creature's natural pelt (fur/feathers or what have they) are considered an acceptable analogue for clothing, thus the subject of them being technically "naked" is almost never mentioned. Many animal characters from The Golden Age Of Animation wore no clothes whatsoever, but acted denuded only when random comic violence rendered them featherless or furless, with their underlying bare skin (and occasional goofy print underwear) revealed.
There are six common ways that cartoon animal characters dress:
Half Dressed:
Pantless or Bare-bottomed: wears a shirt or some other kind of top, but no pants, skirt, or overalls. This also refers to characters wearing dresses or skirts with shirts but without underwear.
Shirtless or Bare-chested: wears pants, skirt, or overalls, but no shirt or any other kind of top. Some characters wearing skirts without shirts are not wearing any underwear.
Accessory Wearing: wears some sort of accessory, like a hat, gloves, a bow, tie (or bowtie), a necklace, a collar, e.t.c., or socks and/or shoes, but is otherwise, well, naked.
Barefoot, but Otherwise Fully Dressed
Fully Dressed and Wearing Footwear (Usually Shoes)
Shirtless or Bare-chested: wears pants, skirt, or overalls, but no shirt or any other kind of top. Some characters wearing skirts without shirts are not wearing any underwear.
Accessory Wearing: wears some sort of accessory, like a hat, gloves, a bow, tie (or bowtie), a necklace, a collar, e.t.c., or socks and/or shoes, but is otherwise, well, naked.
Barefoot, but Otherwise Fully Dressed
Fully Dressed and Wearing Footwear (Usually Shoes)
Completely Naked
