Revealing mistake: Peter Sam is already missing his whistle even before it gets knocked off by the branch.
Continuity mistake: When Rusty arrives on the Other Railway, chains are seen hanging beside the signal box, but in the next shot when Rusty asks, "Ooh! What's that?", the chains have disappeared.
Continuity mistake: When Bulgy is driving on the road next to the rails, Thomas can be seen pulling a train instead of being repaired at the foundry.
Plot hole: When Duck and Diesel leave the shed, Diesel follows Duck instantly, but the tracks they are on both lead to the turntable. As they are on different tracks to each other, it would be impossible for Diesel to follow Duck that quickly as the turntable could only be set to one track at a time.
Continuity mistake: Despite Henry's issue from "Coal" in Season 1 being resolved after the crash in "The Flying Kipper", also in Season 1, Henry needed special coal again from "Thomas and the Magic Railroad" until Season 16.
Visible crew/equipment: As Peter Sam passes Skarloey and Rheneas, a camera shadow is seen.
Thomas and the Missing Christmas Tree - S2-E26
Visible crew/equipment: In the scene of Donald and Douglas going out of the yard, a camera tripod can be seen in the top left corner.
Character mistake: The narrator says, "some trucks were left behind", but only 1 truck was left behind.
The Sad Story of Henry - S1-E3
Revealing mistake: When the passengers try to pull Henry out of the tunnel, they have putty on their feet. Sir Topham Hatt's hand is also purple.
Bye George - S5-E7
Audio problem: Gordon has Duck's whistle sound before he crashes into the truck.
James and the Red Balloon - S6-E15
Continuity mistake: When Percy arrives at the docks, he is carrying some freight cars. But when Thomas leaves the cars Percy was carrying disappear.
Other mistake: When Thomas is uncoupled from Annie and Clarabel, he has Percy's face.
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 James passes Edward at Knapford, Edward's train does not have a brake van. But two shots later, it does.
Edward, Gordon and Henry - S1-E4
Visible crew/equipment: When Gordon backs on to the siding, you can see the inside of his cab, which is just some equipment.
Visible crew/equipment: In the scene where James pulls up beside Gordon, studio equipment is visible in the top portion of the screen.
Continuity mistake: The sign says: "Danger - engines must not pass this board." When Thomas passes it, "board" is replaced with "point."
The Sad Story of Henry - S1-E3
Audio problem: When James is about to puff away from Henry's Tunnel, if you listen closely, James is heard puffing before he has even left. (00:10:00)
Thomas and the Breakdown Train - S1-E7
Revealing mistake: In the scene of James' wheels sparking while passing Tidmouth Sheds, a metal rod is igniting the sparks from his wheels.
Audio problem: When Arthur arrives at the lake, he has Spencer's whistle.
Answer: He was in the water.