Thumper is a heavy-duty quarry machine with two arms and caterpillar treads. He is used for loosening rocks. He is laid back in approach with a "cool dude" attitude, though he can come across as accident-prone. His manner is cool, and no job is too big for him. His old work place, The Sodor Mining Co. AKA Boulder Quarry was closed down some time after the events in the Thomas & Friends episode, Rusty And The Boulder, so he was brought to Crotoonia to help work at the Cliffstone Mountain and Baseline Quarries. He has no original voice due to him never getting a speaking debut. Although, an impression of Brian Drummond as George in the series Dinotrux would be a fitting tone for Thumper, or at least something close to it.