Continuity mistake: When Emily and Whiff pull the rubbish trucks away, Whiff is coupled up to Emily, and Emily is coupled up to the trucks. When they pull them away, their buffers are separate.
Revealing mistake: When Edward is at the last station, his whistle is crooked.
Continuity mistake: At the beginning, Edward is pulling 5 cattle trucks. When he approaches the cows, he is pulling 4 cattle trucks.
Continuity mistake: Gordon's express train has 1 composite coach and 2 brake coaches when he passes through Wellsworth station. When he crosses the viaduct, he has 2 composite coaches and 1 brake coach.
Revealing mistake: After Gordon stops on the bridge for the cow, his wheels keep moving for 3 seconds.
Revealing mistake: When Percy stops on the bridge, white glue is on his middle lamp iron.
Continuity mistake: Gordon can be seen next to Edward when Edward says "two big engines afraid of a cow?", but Gordon should have been on the turntable.
Revealing mistake: Edward has wonky eyes in some scenes.
Other mistake: The episode's title in the original PBS Broadcast version is "The Old Iron Bridge" but the bridge was made of wood.
Visible crew/equipment: When Diesel is on the turntable, camera equipment is reflected in the windows for several moments. (00:02:00 - 00:10:00)
Visible crew/equipment: When Bill and Ben are shunting, we can see hands. (00:02:00 - 00:10:00)
Thomas and the Billboard - S12-E1
Other mistake: In the opening scene when Edward and Henry can be seen going into Knapford, Henry is wearing Gordon's face mask.
Other mistake: When James crashes into the tar wagons, Sticky Tac can be seen on his tender.
Thomas and Percy's Christmas Adventure - S3-E26
Audio problem: When this episode was re-narrated in the US, it was changed to an episode about Thanksgiving. This caused a scene to get cut, which messed up the dubbing track, making half of the episode out of sync. (00:03:00)
Revealing mistake: While the passengers are evacuating the station, the platform moves, a pillar in the background moves, and putty can be seen on the platform (stains of it) and on some passengers' feet.
Audio problem: In the extended Season 19 version of "Engine Roll Call," Henry's whistle sound is out of place as it can be heard during Emily's part of the song. Also, Henry is not mentioned in the Season 22 version of the song, but his whistle sound can still be heard.
Thomas, Percy and the Squeak - S6-E21
Continuity mistake: When Percy arrives at Brendam, his steam platform is visible and some of the steam from his funnel disappears, indicating a film cut.
Thomas, Percy and the Squeak - S6-E21
Other mistake: When Alicia the mouse is inside Clarabel, she is missing her forepaws.
Thomas, Percy and the Squeak - S6-E21
Visible crew/equipment: When Thomas arrives, his steam platform is visible.
Continuity mistake: Throughout Season 4, Henry is painted in two different shades of green.
Answer: Breakdown trains help the engines back on track.