Big Mac and Cheerilee?! That's gonna put a damper on the Fluttermac fans...and I kinda felt in sliding in that direction myself...
Oh, but the Doctor Whooves and Derpy...that is one of the reasons why I don't like Twilight being his companion. That and Twilight already has her story and she has Equestria to keep up with (so long as there are no Daleks, Cyberponies, etc. etc. etc). And Derpy is just a "different direction" in the range of companions, somewhere around the Donna angle (Donnaaaaa <3)