Santa Claus

Santa Claus — also known as Father Christmas or, according to the Eleventh Doctor, "Jeff" or "Geoff" — legendarily distributed presents to good children on Christmas morning under Christmas Tree. He played an important part in the Christmas tradition on the planet Earth. The origin of Santa stemmed from a number of different centuries-old traditions, with the most iconic version of Santa being finalised in the early 20th century.

Appearances
In order to deliver presents to all children in a single night, Santa used time loops and clones of himself. (ST: The Man Who (Nearly) Killed Christmas)

The First Doctor visited Santa Claus in his workshop and helped save Christmas. (TVC: A Christmas Story)

The Second Doctor warned Santa of a future where the toy workshop spanned over two thousand worlds and the fabric of space was being torn by his time looping. A solution was found involving a fleet of robot Santas and newly calculated, more stable wormholes. (ST: The Man Who (Nearly) Killed Christmas)

The Fourth Doctor dressed as Santa and snuck into the Brigadier's house with Romana to leave him a Christmas present. (ST: Special Occasions: 3. Better Watch Out, Better Take Care)

Santa helped Iris Wildthyme save Panda from Mary Christmas. (BFIW: The Claws of Santa)