I posted the pilot cartoon for what would become the Cartoon Network hit series Adventure Time. Another CN series I've sampled lately is The Regular Show. This series showcases the wacky adventures of Mordecai the blue jay and Rigby the racoon as they work in a privately owned city park, along with a staff of similary strange beings, such as a gumball machine, ghost, and lollipop-shaped people.
Like Adventure Time, the characters had origins in earlier, amateur-made productions. Here are two of the earlier appearances made by Regular Show creator J.G. Quintel. Quintel made these cartoons while a student at the California Institute of the Arts. The characters themselves are largely different, but the designs are very similar. WARNING: CONTAINS STRONG LANGUAGE AND ADULT THEMES!!
Here is an early sighting of the character Pops in "The Naive Man from Lolliland."
Here you see the first sightings of Mordecai and Benson in "2 in the AM PM."
For comparison, here is the first episode of The Regular Show. Thanks!