let me explain in season whatever of doctor who there was a guy called saxon and he hypnotized the world with the sound of drums
and then derpy is doctors assistant and well there you go
In Season 3 I think an evil Timelord called the Master was running in the election to be prime minister. He hypnotized the people into voting for him with the four beats, the drums that forever go in his head. He attempted to take over the world with future humans, but was stopped by the Doctor and his companion Martha.
Derpy Hooves met the Doctor when he first arrived in Equestria, and she became his first pony companion.
So, I know my Doctor Who xD So I know who he is and everything, but I don't get why Derpy's in his bed xD