It feels like I've always doodled and drawn cartoons. I have a vague memory of a cartooning class or section in art class or something, and then of course I worked for Pixar. For me, it comes down to familiarity and practice. For that reason, I can do a half decent sketch of most Pixar characters.
A long while ago, I obsessed over getting the Sword-in-stone squirrels right, and now recently I've decided to start working on Disney characters again. Why? I think drawing is an important skill for communication, and like with writing and speaking, you have to practice it; cartoons are a facet of that. Why Disney? Disney is well-known and easily recognized. The characters are simple and well-crafted, and so it's a good learning tool. Plus, I've fantasized about doing a webcomic.
My first attempts were heinous, but tonight I did a somewhat passable Belle. With time...*sigh*... I feel like I'm a teenager again.
My old Disney squirrel studies: