A fantastic cartoon about a human boy named Finn and a stretching dog named Jake and their adventures in the land of Ooo. Sometimes there are penguins.
Mathematical! Rhombus!
It began with a short animation of the same name and eventually was developed into at least five seasons of 26 11-minute segments each. The episodes generally focus on a moral, such as helping others or trusting your gut. It has great voice work, whimsical animation, and many hilarious moments.
Adventure time, c'mon grab your friends; we're going to very distant lands. With Jake the dog and Finn the hu-man, the fun never ends; it's adventure time!
<Finn> Jake! That horse is whack with poo brain.
<Jake> Yeah, I know Finn, I diagnosed this horse with whacked out poo brain five minutes ago.
Did I mention the post-apocalyptic subtext and great arching backstory?