Thomas and the U.K. Trip & Thomas Number 1 (found Japanese Thomas the Tank Engine crossover and music video; 1993)
Thomas the Tank Engine has had many specials, and most believe the first was Thomas and the Magic Railroad. However, in 1993, the true first Thomas special aired, a crossover entitled Thomas and the U.K. Trip, featuring characters from the Japanese show, Hirake! Ponkikki. The characters from the Japanese show visit the Island of Sodor where Thomas and his friends live, and then the "real" UK to see real steam engines. The special was never released on VHS, however, it is most likely that it was recorded by a home viewer, as the whole special is on YouTube.
Interesting enough the "I'm Thomas the Tank Engine" music video had been released on a Japanese VHS called Hello Thomas and James (Pちゃんのハロートーマス＆ジェームス) back in 1996. Another rare Japanese Thomas artifact is the song "Thomas Number 1". It is so obscure that it is not listed in the songs category of the official Thomas the Tank Engine Wiki. It's confirmed as to be an official music video made exclusively for Japan as at the time the first two seasons had aired in Japan. The music video uses clips from seasons 1 and 2 which had only aired at that very time during this specials airing. (The song currently credited as the first is "Thomas' Anthem").
On October 16, 2016, the special was found and uploaded onto YouTube by ThomasFan1945 Productions™.