Thomas, Edward, Henry, Gordon, James, Percy, Toby, Annie, Clarabel, and the Fat Controller (known in the American dubs as Sir Topham Hatt) are the only characters who appear in every season of the original series and "Big World! Big Adventures!." Bertie and Henrietta appear in every season of the original series.
In the first 11 seasons, the show used live-action models exclusively. Season 12 used a mix of CGI and models. However, from Seasons 13-24, it was entirely animated in CGI.
Public Broadcasting Service (PBS) aired a spin-off called Shining Time Station (1989) from 1989-1993. This was created to introduce Thomas the Tank Engine to American viewers.
As the narrator of the American version, George Carlin was nervous about recording his narration without an audience, so the producers put a stuffed teddy bear in the booth with him.
Britt Allcroft the creator of the series, picked Sir Ringo Starr the former drummer of The Beatles as the narrator when she heard his voice on television, thinking it would relate to children. Starr narrated the first two seasons of the show.