Doctor Whooves might be canon.
The episode features the Doctor as an official contest timer. Here's a screen grab.
Now, the reason I point this out is because of his neck. The Doctor is wearing a collar and a green tie. So what you ask? Here's an image of the Doctor from back when he was just a regular background character.
Notice, no collar or tie. The collar and tie did not turn up until the fandom started making Doctor Whooves stories and started putting a white collar and green tie on him. And we know the show staff in general and Lauren Faust in particular lurk in all the MLP forums to see what everyone is talking about, as the gag with Derpy as a furniture mover proves.
Is this their way of telling everyone that he's not a generic background pony, he really is Doctor Whooves? No one can say for sure, given that this could be construed as copyright infringement if they admit it.
Nevertheless, I'm going to be watching very closely for a blue police box....