The MLP universe time traveler set was done as a commission for
The pieces have all been posted seperately here, here and here, but a group shot can't hurt. They were designed as a set after all, with the ponies designed to be approximately correct in comparative size, and the TARDIS was made as a carrying box with the shelf up top for their tails and Derpy's wings.
My Little Pony belongs to Hasbro. Doctor Who belongs to BBC.
On an unrelated note:
The removable wings reminded me of this awesome fanfic: [link] If you have some time and want to laugh, read it!