Pudsey

Pudsey Bear 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 search for former companion, by Eddie Redmayne. (NOTVALID: Looking for Pudsey)

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

More info at Children in Need.