Continuity mistake: The children waving at Toby disappear after Toby puffs under the bridge.
Continuity mistake: Alicia Botti was annoyed by Toby's appearance. But in "Thomas, Percy, and the Squeak", she thought Percy being dirty was the proper appearance of a steam engine.
Other mistake: Duck stops at Arlesburgh West Station for 5 seconds, which is not enough time to let passengers board his train.
Revealing mistake: When the boys sing, the camera shakes.
Character mistake: The driver said that Bill and Ben's names and numbers would be taken away, but the twins do not have numbers.
It's Good to Be Gordon - S10-E9
Character mistake: The narrator refers to Henry as "Henry's engine."
Other mistake: The narrator says that the fence was mended, but there is no fence and there never was.
Revealing mistake: In a close up of Edward, he has Thomas' whistle sound and no tender.
Plot hole: James appears in every episode before his introduction in "Thomas and the Breakdown Train." Also, James is supposed to be black, because at the end of the episode, James is told he will get a different coat of paint. (He is also black in the book).
Deliberate mistake: Due to the production order, Arthur can be seen at the quarry, but his introduction is 6 episodes later, in "The Spotless Record."
Factual error: Black smoke comes out of Henry's cylinders, when it should only be coming out of his funnel.
Revealing mistake: When Thomas leaves Dryaw, in the background, the biplane's propeller stops spinning, revealing that the propeller is actually a CD.
Character mistake: The narrator says that Thomas had never delivered the mail before, but he did in Season 4.
Other mistake: Mavis and Cranky should've realised that Thomas woke them up the first time he blew his whistle.
Other mistake: In the very first shot of Spencer, his coaches aren't textured.
The Biggest Present of All - S13-E16
Audio problem: When Henry and James are at the quarry, their whistle sounds are played out of order.
Audio problem: After Rex is hoisted back on the rails, Mike has Rex's whistle sound.
Continuity mistake: Gordon's Hill is much taller and steeper than it usually is. Also, when Belle reaches the other side of the hill, the tracks on the viewer's left disappear.
Other mistake: The Rev. W. Awdry is not credited in the title card of the episodes "Mike's Whistle", "Tit for Tat", and "Useful Railway." Only Andrew Brenner's name appears.
Factual error: At the beginning of the episode, the narrator says that Connor and Caitlin are faster than Spencer, but Spencer, an LNER A4, holds the world speed record for steam locomotives.
Answer: He was in the water.