I think ponies are inherently funny, what with how short and dumpy and angry they are, and I liked it being a pun on Tiny Dancer. Tiny Prancer is also what I put in to replace my real name on google plus, after they merged with youtube and suddenly my real name was on my youtube comments, much to my horror. (I also use it as my name/username on a tabletop rpg site I was playing a game with some friends on, and kept getting messages addressed to "Tiny P." which I thought was super adorable.)