A Friend in Deed

When Pinkie Pie meets Cranky Doodle Donkey, she becomes flummoxed about what to do when the donkey refuses her usual offer of lifelong friendship, so she must decide what to do next about the first creature ever to do such a thing.
My Little Pony: Friendship is Magic - Season 2, Song #7: "The Smile Song"
My Little Pony: Friendship is Magic - Season 2, Song #8: "The Cranky Doodle Donkey Song"
My Little Pony: Friendship is Magic - Season 2, Song #9: "The Welcome Wagon Song"