Pudsey

Pudsey Bear was associated with Children in Need.

Whilst he was in the Blue Peter studio, he was mistook for a minion by Greg James who then apologised. (NOTVALID: Mind My Minions)

He was a temporary companion to the Twelfth Doctor and Clara. He helped defeat Sontarans, Daleks, Colony Sarff and the Mire. (NOTVALID: Doctor Who Game Maker)

The Twelfth Doctor was later contacted, to help in the search for his former companion, by Eddie Redmayne. He was eventually found in Redmayne's briefcase. (NOTVALID: Looking for Pudsey)

Behind the scenes
He was added as a companion for one week during Children in Need in Game Maker.

More info at Children in Need.