This was to be the original pilot for the show Adventure Time on Nickolodeon. However, it was never turned into a full time show, but was later picked up by Cartoon Network. This short tells the story of Pen and his dog friend Jake on a mission to save the Princess from the Ice King.
Personally, if any of you have seen the new episodes on Cartoon Network, I don't recommend it. This short is so much less trippy than the popular kids' show the public now knows as Adventure Time. This short has much better humor and doesn't heavily rely on the strange narration that the new show does. Maybe I'm spoiled by seeing this before the new show came out, but I still think this does a much better job of portraying Pen and Jake's adventures.
While the animation itself is not all that fancy or advanced, it does the job of creating an interesting world for Pen and Jake to explore. It's weird enough to make the show not too cliche, but it's not as bizarre as the newer version. This short is able to get across what it wants to without relying on overstimulating its audience.