Percy is a green saddletank engine. He is the No. 6 engine on Sir Topham Hatt's Railway and is best friends with Thomas and Toby.
- Season 1: Stepney's Problem, A Scottish Tale, Toby and the New Engine, Duties of the Diesels (cameo), Wilbert to the Rescue, Wilbert and Tiger Moth (cameo), Frank and the Trucks and Gordon Plays a Trick
- Season 2: Daisy and the Visitor (cameo), James' Tender Trouble, A Flying Surprise (does not speak), Twin Trouble (cameo), Old Slow Coach (mentioned), The Flying Scotsman Returns, Save Sir Topham Hatt!
- Season 3:
- Season 4: Rosie's Wild Ride
- Season 5:
- Season 6: Percy's World Record
- Season 7:
- Season 8:
- Season 9: Tender Bender
- Season 10: Bee Yourself, James, Mike Goes on Strike, Coal Crisis (cameo), and Groundhog Gordon
- Season 11: Big City Rumor, Duncan in the Dumps (cameo), Just Duck's Luck, Spencer Goes Too Far and Holly Jolly Molly
- Season 12: Percy Gets a Promotion, Henry's Handcar Havoc (mentioned)
- Season 13: It's Good To Be Belle (cameo), Victor's Loco Motives, Who Stole The Coal?, Ivo Hugh's Day at the Zoo (cameo), Hector and Logan's Hot Pursuit and How Gator Stole Christmas (cameo)
- Season 14: Double-Decker-Wrecker (cameo), Hiro and the Heat Wave, Furious George,