For me, 'Thank You' is the shining example of "Adventure Time"'s ability to move you when you least expect it . . . and it involves almost no involvement from Finn and Jake and just about as many spoken words (but still has one of my favorite lines from the show: "Ice King, this is the last time you steal our sandwiches!"
This one's all about the Snow Golem who, for the most part, is a one-off character. Golem gets stuck with a wayward fire wolf cub, which is no picnic for the big guy; that wolf can kill him. Which is what makes their unlikely bond so endearing. In this cub, he finds companionship in an otherwise solitary life - as well as the need to get this cub back to its family, and he ventures straight into fiery pits to do so.
It's a very simple story, but one that speaks to the power of kindness and friendship that one person can instill when you least expect it. And there's some very pretty animation here, as well. It's sweet, funny, and just warms your soul.
10/10