A Bad Sight is the 27th episode of Season 5 of Thomas the Tank Engine & Friends.
Aaron, the stubborn, rough-mannered tank engine, was resting in a siding at the station when Thomas comes furiously by, waking him up with biffing him up. This makes him cross, as Thomas pulls him to the yard where a long, heavy frieght train is. Percy tells Toby about big accidents, and this only makes Aaron more cross when he finds he has to pull a frieght trains, making him angry. Donald pulls a frieght train to the harbour. Aaron follows with a longer frieght train a few minutes later. He pulls it through the countryside, but on the way to the mountain, subsidence in the trackbed caused by a thaw of frost on causes him to mount the rails. His piston lifts clear of the rail, causing him to lose all his brakes. Aaron gathers speed down the line and goes up a mountain. His driver and fireman jumps clear, but Dr. Eggman, his caretaker, can't because he is trying to find the lost brakes, and the frieght train is halted by the brakes, aids by the action of the handbrake, and stays on the rails. Aaron comes off the rails, plummets, landing in the valley far below, completely wrecked. And Dan had been thrown clear, giving himself a headache. The conductor, as he applied the cars' handbrake shouts. However Aaron damages a telegraph pole on his fall, disabling all communication between Crovan and the summit itself. Toby must take Aaron's frieght cars to the station. Aaron is never replaced, nor his his number 4215 uses for any other engine. Services are suspended for another year till the track was repaired.
- Annie and Clarebel (do not speak)
- Sir Topham Hatt (mentioned)
- UK Narrator: Michael Angelis.
- US Narrator: Alec Baldwin.
- The Season 4 Thomas the Tank Engine & Friends Musical Arrangement used in this episode was also heard in "Rusty To The Rescue".
- When Aaron tumbles off the cliff and crashes into the valley below, the crash sound is a mix of the one from "Running Out of Steam" (when the flying womble train crashes) and the one from "The Flying Kipper" (when Henry crashes into the breakvan and lands on his side).
- The mountain set used in this episode was silimar to the Narrow Gauge Season 4 one, except it has standard gauge rails and has more rocks.
- During Aaron's runaway scene, the Season 3 Thomas & Friends Runaway Theme is used.
- Alec Baldwin: One morning, Aaron the stubborn, rough-mannered tank engine was resting on a siding at Elsbridge station.