Theo

Theo is a shy experimental railway traction engine who works at the Steelworks on the Mainland.

Trivia

 * It is said that Theo displays personality traits of autism, making him the first Thomas & Friends character with a neurological disability.
 * Theo speaks with a mild lisp, therefore also being the first Thomas & Friends character with a speech impediment.
 * Similarly to Fergus, a semicircle has been cut into Theo's front bufferbeam to accommodate a face.
 * On the back of the Journey Beyond Sodor DVD, Theo's lamp is white instead of gold.
 * Theo is the second traction engine to run on rails, the first being Fergus. However, including non-rail traction engines (not counting George and Buster), Theo is the third traction engine introduced to the series.
 * Theo fretting and saying "I think I can't, I think I can't," is very similar, if not a direct reference to the famous children's book "The Little Engine That Could."
 * He is the smallest experimental engine.