Doctor Whooves

Doctor Whooves is a pony popular with the show's fanbase. Because he does not have an official name, there are several alternate spellings, including "Doctor Whoof".

His spiky brown mane and his hourglass cutie mark lend him the appearance of the Tenth Doctor from the popular British TV series Doctor Who, hence the moniker, which originated on the /co/ board on 4chan. The name was eventually (unofficially) adopted by the show's crew.

He is often imagined to have a British accent, despite pieces of dialogue in the actual show (Call of the Cutie and ) showing no traces of this.

In fan labor, Doctor Whooves is often accompanied by a companion, just like in the TV show. Examples include Apple Bloom (likely due to their previous interaction in Call of the Cutie), Twilight Sparkle, and Derpy Hooves. Beyond fan art, there is also a notable series of audioplays (link to episode 1) and some pieces of fan animation (e.g. these two by enquaynay).

THE Doctor
This is the most common version of Doctor Whooves, especially in works where he is the primary protagonist. Due to a dimensional mishap with the TARDIS, the Doctor is transported from his home universe to the My Little Pony universe and either undergoes regerenation or is simply transformed by the universe's equine-centric laws. In either case, he then goes on to have a typically Doctor Who adventure with whatever companion(s) he picks up and has all his usual equipment and off-beat... Doctor-ness. Who-verse aliens and monsters typically show up either as they normally are or altered to fit the equine/four-legged model.

Gallopfreyean
Sometimes Whooves isn't from another dimension, just the pony-verse's version of Gallifrey,"Gallopfrey". This version allows for multiple Doctors to exist without paradox (i.e., the "humanoid" one warps into Equestria and works alongside the equine one).

Alternatively, he's not technically an alien pony, just a strange one who may or may not posses a time machine or power over time. He's usually an incidental or side character in this model.

Colt Smith
Occasionally he is seen as a semi-background character where his involvement is merely hinted at. In these cases the residents of Ponyville usually know him under an alter-ego. (Much like the actual Doctor often used the name "John Smith" to blend in.) There are also times when he is portrayed as a pony who actually believes this alter-ego, due to his Time Lord(/Pony/Colt) self having been stored in a Fob Watch. (A special device used to store the essence of a Time Lord, allowing them to become a different person in their mind and change their physiology to a different specie's.)

Doppleganger
He is NOT Doctor Whooves! And yet everypony thinks he is...he's just another Ponyville citizen who happens to have an hourglass for a cutie mark. He's probably a clockmaker or something like that. Simple, sensible, and frankly not nearly as interesting as the Time Colt versions.

Example: Sepia Tock

The other Whooves
There are other ponies in the show with the same hourglass cutie mark. Due to this repeated use of the cutie mark, some fans believe these ponies are regenerated versions of him or his companions. One attempt to match ponies and Dr Who characters can be found below.