Mr. Percival (a.k.a. the Thin Controller) is the director of the Narrow Gauge Railway. He has a wife and five children. He idolizes the Fat Controller, and he tries to manage his railway like he manages his. He will even say "You have caused delay and confusion" when an engine goofs.
- His first name is Peregrine.
- He despises cars, so he rides his bicycle around his railway.