Percy is the best friend of Thomas. Percy has many jobs on Sodor, but his favorite is carrying the mail.
As the television series has progressed, Percy has been dumbed-down in order to teach viewers difficult words: he would say "dingy-fried" where anyone else would say "dignified". He is also shown to make obvious mistakes.
Percy is incredibly accident-prone and holds the dubious record of the most accidents in one season - five, in the second season - crashing into some buffers, falling into the sea, being pushed onto a brakevan, colliding with a cart, and being hit by a falling crate of treacle. So far, his silliest accident yet was in the sixth season, when he slipped on oily rails, crashed through the chocolate factory, and emerged covered in chocolate.
Since the second season, Percy has had a small rivalry with Harold, stemming from their race. However, they are always willing to help each other when in trouble.
Percy is primarily based on an Avonside 0-4-0ST with the body of GWR 1340 Trojan, the bunker of GWR 1361, Hunslet underframes and valve gear, a smokebox protruding from his saddletank, external cylinders and motion, and sandboxes underneath the tanks on his footplate.
Percy is painted NWR green with NWR red-and-yellow lining and a "6" painted on his bunker sides in yellow.
In the Railway Series, he carries two builder's plates, one on either side of his cab.
- Michael Angelis (Thomas and the Magic Railroad; original workprints only)
- Linda Ballantyne (Thomas and the Magic Railroad)
- Keith Wickham (UK; Hero of the Rails onwards)
- Martin Sherman (US; Hero of the Rails onwards)
- Chisato Nakajima (Japan; first-eighth seasons)
- Chie Koujiro (Japan; Calling All Engines! onwards)
- Anders Sundstedt (Norway; Hero of the Rails onwards)
- Mattia Nissolino (Italy)
- Javier Olguín (Mexico; Hero of the Rails onwards)
- Robin Brosch (Germany)
- Grzegorz Drojewski (Poland)
- Percy' large scale model used for the spin-off series, The Pack is currently on display in Japan at Thomas Land.
- In Jack and the Sodor Construction Company, Percy's dome is green and the steps up to his foot plate are red.
- Percy was the first character to have merchandise.
- Since the fourteenth season, Percy's whistle budges up and down when he blows it.
- One of Percy's models is currently on display in Canada at Nitrogen Studios.
- In the French version of the Classic Series, Percy was called Pierre, but during the New Series, he is called Percy.
- From the eighth through twelfth seasons, Percy's cab windows were blacked out.