Finn and Jake are exhausted and just want to sleep, but a strange, googly-eyed horse is staring at them from outside the Tree Fort. Their increasingly desperate attempts to get rid of the horse (including playing a lullaby and disguising themselves) fail until they discover it’s actually a costume.
Generally considered filler . While it doesn't advance the main lore, it is often cited by fans as one of the funniest episodes of the early seasons. [S2E2] The Eyes
It is revealed that the Ice King is inside the horse costume, spying on Finn and Jake to learn their "secrets to being happy". Viewing Context Finn and Jake are exhausted and just want
"It Came from the Nightosphere" (S2E1) — A major lore episode introducing Marceline’s father. While it doesn't advance the main lore, it
is the second episode of Season 2 of Adventure Time . In this episode, Finn and Jake try to get some sleep but are haunted by a bug-eyed, staring horse outside their window, which eventually leads to a confrontation with the Ice King. Quick Episode Guide