Sally Cruikshank is a self-taught artist who started making animations in the 1970s. She did a lot of work for Sesame Street, but the stuff I like the most are her crazier cartoons. She cites Busby Berkeley, known for elaborate movie-musical dance numbers and Max Fleischer, known for classic cartoons like Popeye and Betty Boop, as her biggest influences. Examples of their work can be seen here and here, respectively. (You can kind of skip through the beginnings of both, if need be.) Max Fleischer also invented the rotoscope which allowed animators to draw over live-action film to create animation.
"Make Me Psychic"
"Don't Go in the Basement"
I also really like "Quasi at the Quackadero" which is on YouTube. It's about a trip to an amusement park in the future. Sally's blog is here.