Revealing mistake: In a close-up of Thomas at the beginning of the episode, his wheels aren't moving for 2 seconds. This is easier to see in the restored version.
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.
Revealing mistake: In the first close-up of the policeman, the camera wobbles.
Revealing mistake: When Henry arrives at the forest where he finds his lucky trucks, one of the trees is not covered in snow.
Revealing mistake: The waves hitting the ship are obviously being sprayed by a hose.
Wrong Road - S2-E22
Revealing mistake: When Edward crosses the viaduct, the last coach of his train does not have lighting.
Thomas, Terence and the Snow - S1-E13
Revealing mistake: When Thomas gets dragged out of the snow by Terence, he is still covered in snow all around him, but two shots later, the snow has vanished.
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
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.
Thomas the Jet Engine - S6-E22
Revealing mistake: After Cranky unloads the jet engine, it is already turned on.
Revealing mistake: When the boys sing, the camera shakes.
Revealing mistake: In a close up of Edward, he has Thomas' whistle sound and no tender.
Revealing mistake: When Thomas leaves Dryaw, in the background, the biplane's propeller stops spinning, revealing that the propeller is actually a CD.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: In the very last shot of the episode, Thomas and Stanley are faceless.
Revealing mistake: In a close up of Gordon after Rocky clears the tracks, Gordon has wonky eyes.
Revealing mistake: When Gordon is being pulled from the pond, in the close up scene of Gordon reversing up the sleeper bed, the front of his buffer beam/running board catches on the upright stake to the right hand side of the worker figure, pulling it back before it rights itself. (easier to see on widescreen version). (00:04:10)
Revealing mistake: In a shot of Gordon arriving at Brendam Docks, only half of his tender is visible.
Revealing mistake: When the passengers lift Duncan back onto the rails, his trailing wheels are still derailed.
Thomas' Christmas Party - S1-E26
Revealing mistake: In the very last shot of the episode, loads of wires are visible in front of the engines and behind the turntable.
Answer: He was in the water.