Double Trouble
S13, E4: Thomas is sent to pick up the Fat Controller to take him to a birthday party. However, when he arrives at the station, the Fat Controller seems to have been replaced by a mischievous impostor.

S13, E4: Thomas is sent to pick up the Fat Controller to take him to a birthday party. However, when he arrives at the station, the Fat Controller seems to have been replaced by a mischievous impostor.