So many Unicorn parties!

Summer

I have a sincere question here. I'm wondering how unicorns became so popular? It seems like every little girl these days is having a unicorn party. Is there a tv show or a unicorn character that I don't know about? (I have a 1 year old so I dont know much about the kid culture yet!) Is it just that they're colorful and pretty? Or do they just get the idea from their friends parties and want to do the same? Or something else??