In my headcanon Derpy is slightly younger than Rainbow Dash and they used to be friends in flightschool. When other ponies were bullying Derpy for not being able to fly straight directions, Rainbow would always stand up for her and defend her.
No shit sherlock is simply a joke for when people are being obvious. You were being obvious (like a few people before you.) And I didn't mean to offend you. Sorry, I don't enjoy repetetive comments that don't really hold anything about the art itself, which is kinda the point. Don't be offended, I was making a funny.
Thanks for pointing that out. I didn't know it was a simple joke. I'm just one of those people who are "late" in the sayings (not to mention songs) like that one: "no shit Sherlock". Sorry for the misunderstanding
Then about everypony in ponyville other than the Mane 6 would be elderly by now. It's simply because they recycle their backgroundponies, no matter what time the scene plays in. There is also a filly Derpy in the Cute Pox episode.