Pinkie Pie is the earth pony representing the Element of Harmony, Laughter. She is literally a party animal, she'll throw a party and follow up with an after-party party. She doesn't care about the laws of physics or the fourth wall; she does what she wants when she wants. Sonic Rainboom? Try Pinkie Pinkboom. She can randomly spawn other ponies at will and force them into musicals they would otherwise not partake in, she can both fly and perform magic despite being an earth pony, and she is friends with everypony she knows! There may be some sort of correlation there... Friendship is magic after all.