Greetings, welcome, and hello to all! Welcome to our second ever Special Episode! For this round, we will be talking about cartoon animals who are assumed to be equivalent to humans, specifically on how the females tend to be treated in those cases.
For our first day, we need to address a singular topic: What makes a cartoon animal a girl? This is a little harder than you might realize, while still easier than you think.
Humans can easily tell males and females of their own species apart. It's the reason we laugh at Professor Oak asking if you're a boy or a girl: the fact should be plainly obvious. It's also the reason why a popular trick played on the internet is to present what looks like a cute girl, only for them to turn out to be a man: We know what girls "should" look like, and it's quite a shock to see that what looks like a girl isn't.
That same courtesy cannot be said for animals. With no training whatsoever, I want you to do an image search for an animal, just by the name of the animal and nothing else. Look at any real life photo. Can you tell if the animal is a male or a female? You probably can't, and if you can you would have had to have looked it up in some kind of guide previously.
So since cartoons that star animals need some kind of females in their cast let it become a Boys Club, we need ways for the audience to easily tell whether or not the character is a boy or a girl.
This leads to something we call "Tertiary Sexual Characteristics". What are those? They're things that signify something is a girl without any sexual content, stuff like the color pink, ribbons, or a skirt. It may seem a little sexually backwards, but unless you can think of another method to tell a young cartoon animal girl apart from the boys other than her voice, you kinda need them. It's a necessary evil.
Now, fully-dressed cartoon animals like the characters from Star Fox don't need these. Krystal can dress up in a military outfit and be equal to Fox's outfit. But in cases where the animal is not fully-dressed, or even dressed at all, Tertiary Sexual Characteristics are kinda needed. 
Take Tiny Toons Adventures, for example. Males will often go bottomless, sometimes even have no clothing, and the girls need to look similar. Thus, even in cases where they have nothing on, they still have things like, say, a bow or a pink color scheme. It actually makes sense with Buster and Babs; one's a blue bunny boy, the other's a pink bunny girl with a skirt. Their gender is easily identifiable. These girls didn't need clothing; Fifi La Fume is still purple despite never wearing anything. It's just the boys are dressed, so the girls get something, too.
There's a similar case with another WB cartoon, Animaniacs. The two boy Warner Brothers have some boyish outfit, while Dot, the girl, has a skirt. No shirt is needed, the skirt does all the work. It gets the job done simply and easily. Rita and Runt are also good examples, since their designs easily convey "masculine and feminine".
So the first element that unites this entire topic is "A girl needs to be, above all else, recognizable as a girl." Tune in next time when we see how this relates to the Law of Equivalency.