Revealing mistake: When Thomas leaves Dryaw, in the background, the biplane's propeller stops spinning, revealing that the propeller is actually a CD.
Other mistake: The narrator says "the road left the railway...", but there is a road right next to Thomas.
Tenders and Turntables - S1-E15
Visible crew/equipment: In the close-up of James spinning on the turntable a crew member's face is reflected in his paintwork.
Revealing mistake: In a close up of Edward, he has Thomas' whistle sound and no tender.
Continuity mistake: When Edward is pushing trucks over a turntable, when he stops, he is very close to the trucks, when the camera changes, he moves back a bit. (Note the tank the Fat Controller is standing on).
Continuity mistake: Before Percy Runs Away, his crew is out of the cab. But after Percy Runs Away from Gordon, his crew is back in the cab.
Character mistake: In the shot of Gordon pulling Percy, he is congratulating Percy, but Percy didn't stop the accident, Gordon himself did. Percy didn't try to get out of the way, Gordon had to put his brakes on as hard as he can. So why is Gordon congratulating Percy?
Revealing mistake: In a shot of Henry going around a bend in the country, you'll notice that the other side of the coaches is seen painted tan but the other side is painted green and white. This is because of budget limitations.
Continuity mistake: US Only: Henry reverses on to the siding, then he leaves it again. His tender also hits the station building.
Visible crew/equipment: As Henry crashes into the goods train, a crew member's hand can be seen pushing him, at the left side of the screen.
Continuity mistake: When Henry leaves the docks, there's nothing on his footplate, but when he's out of the docks, there are suddenly 2 lamps on his footplate.
Visible crew/equipment: As Henry approaches the green signal, the edge of the set is seen in the distance.
Continuity mistake: When Henry sneezes at the boys, you can see that the boys got ashes on them before the smoke has even touched them yet.
Continuity mistake: When Henry sneezes at the boys, in the shot of the boys with the smoke rising up, you can see that they already got ashes on them before the smoke had even touched them.
Character mistake: The narrator says that the passengers covered their ears at the station, but no one is covering their ears, except Sir Topham Hatt.
Toby and the Stout Gentleman - S1-E21
Revealing mistake: When Toby and Sir Topham Hatt are at Lower Arlesdale, Toby's face is loose.
Toby and the Stout Gentleman - S1-E21
Other mistake: Toby passes the Post Windmill twice, but that is on Thomas' branch line.
Toby and the Stout Gentleman - S1-E21
Revealing mistake: In a close up of Sir Topham Hatt, the camera shakes.
Toby and the Stout Gentleman - S1-E21
Revealing mistake: The water is not flowing when Toby passes Arlesdale Lake.
Audio problem: When Sir Topham Hatt, the policeman, and Thomas' crew are at Elsbridge Station, Thomas whistles, but his crew is standing on the platform.
Answer: Breakdown trains help the engines back on track.