here are the three original shorts that the popular Nickelodeon television show "Hey Arnold!" was based on -- all by Craig Bartlett while working at the Will Vinton Studios. the first one and arguably the best is "Arnold Escapes From Church" from 1988. its got a great flat clay aesthetic.
coincidentally that Groening you see in the credits is Lisa Groening -- Matt's sister and Craig Bartlett's wife. Vinton was notorious for encouraging his animators to make short films. Hey Arnold! in particular started originally as a comic strip. here's the next short, "The Arnold Waltz" -- it shows a little bit more of the rest of the characters in the later series, though it continues the idea of a very daydreamy Arnold:
this last one was featured on an episode of Sesame Street. once again, not much to say, just very inventive. i'd love to animate clay on glass some day -- Rex the Runt did it beautifully.