Why cry? it's motherfucking Derpy! give her lots of hugs and muffins

It's from the episode when lisa get a horse.
when she wake up, she find a horse that homer secretly put in the blanket the night
and lisa scream out of terror. but after that she became happy and the rest is another story.
oh, and im not sure if its 100% accurate what I just said and I don't remember if it's a horse or a pony.