Thomas the Tank Engine "The Missing Coach"

"The Missing Coach" was a scrapped episode of Thomas the Tank Engine based off the Railway Series story of the same name that was intended to be the sixteenth episode of Season 2

Plot
"The Missing Coach" saw the arrival of twin engines Donald and Douglas, having been ordered from Scotland by the Fat Controller; the twins soon discover that only one engine was sent for and that the other would not be needed (and would likely be sent back). Douglas and his driver, after realizing that Douglas is, in fact, the extra, unneeded engine and after mistakenly misplacing Thomas' Special Coach, prompting complaints from passengers (Douglas fearing that his error would give the Fat Controller more reason to get rid of him), hatch a plan with Donald and his driver to switch tenders (on which their respective numbers had been painted), effectively swapping identities and giving Douglas a chance to temporarily avoid being scolded by the Fat Controller (who ultimately decides to keep both engines, but only after uncovering their charade).

Cancellation and Existence
Halfway through the episode's production, Britt Allcroft (creator of the Thomas TV adaptation) decided that it was somewhat lacking in action and that the plot was a bit too complex for children to comprehend; as such, the episode was cancelled outright, instead being replaced by an entirely different episode, "Thomas, Percy and the Coal". Donald and Douglas' official series debut took place in the later Season 2 episode "Brake Van", in which they were hurriedly introduced through a short piece of opening dialogue; it has been speculated that the opening scene from "Brake Van" may have been retooled footage originally shot for "The Missing Coach".

On a Sodor Island Fansite interview with the late David Mitton (who co-wrote, co-produced and co-directed the show up until his retirement in 2003), published after Mitton's death in 2008, he confirmed that he was in possession of a collection of color stills from the episode's shoot (as shot by Terry Permane), although, as of his passing, the fate of said stills has not been revealed (though they have likely been handed down to Mitton's heirs); the fate of the shot video footage is, likewise, currently unknown.