Originally there was supposed to be a character named PT Boomer, who is trying to buy Shining Time. This character was cut from the final film, however you can see him laying on the back of Diesel 10 in certain shots, as his character was in the final chase.
Michael Angelis, the narrator for the United Kingdom version of Thomas and Friends was originally cast as the voices of James and Percy. After the American test audiences heard his recording, his part was deleted as it made the characters sound too old. The roles went to Susan Roman and Linda Ballantyne respectively.
Isle of Mann taxi drive/firefighter John Bellis was originally cast as the voice of Thomas. After his recording was heard by American test audiences, they disliked his Liverpudlian tone as it made Thomas sound too old. The role went to 'Eddie Glenn'.
Despite the removal of PT Boomer (played by Doug Lennox), his character does appear during the film. Originally taking part in the final chase sequence, extensive editing had to be done to trim down the shots where he rides on the back of Diesel 10.
People that worked on the original series also worked on this movie, namely, David Mitton (as model unit creative consultant), David Eves (as model SFX supervisor), Steve Asquith (as model supervisor), and Terence Permane (as director of photography for the models section).
Brian O'Connor was asked to reprise his role of Schemer from the television series, but turned it down based on his decision to retire from on camera acting. Jim Carrey was not available for the role because he was busy acting as the title character in Universal's production of How the Grinch Stole Christmas (2000). For these two reasons, Schemer is entirely absent is this film.
Keith Scott was originally cast as the voice of Diesel 10. After the American test audiences heard his recording, his part was deleted as the character sounded "too scary". The role went to Neil Crone, who improvised much of his dialogue and originally voiced the character with a gruff Russian accent. However, someone was worried this may offend some viewers, so he redubbed his lines with a New Jersey accent.
In the movie, several aliens can be seen in the background of the film- a joke by the creative team as they made the movie come alive with CGI. The producer, Britt Allcroft, touched upon it once in an interview dismissing it as a funny morsel for the parents.