"I'll not let it happen again..."
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"We are experimental engines!"
— Theo, Journey Beyond Sodor


  • Configuration: 0-4-0

Theo is an experimental railway traction engine.


When Thomas travels to the Mainland, he befriends the experimental engines, Theo, Merlin and Lexi. Later, the experimental engines come to rescue Thomas and James when they are trapped in the Steelworks.


Geared engine Theo is very shy, extremely cautious and awkward. He has an unusual experimental drive system that doesn’t always run very smoothly, and he makes sudden jolts forward or back when his rods or cogs jam. Quiet and thoughtful, with a habit of blunt speaking, his confidence is often jolted. But Theo is genuinely kind and caring and would just like to keep himself and his friends as safe as possible, so they can hide away and have a quiet life.”


Theo is based on the railway traction engines. His precise basis, however, is unknown.


Theo is painted greyish brown with gold lining, head lamp and whistle. His wheels and lower traction wheels are dark green while his upper traction wheels are a redish brown. Theo also carries his name on gold nameplates fixated on each side of his smoke box.


Television Series

Thomas the Tank Engine & Friends


Other Media

Voice Actors

Songs Performed


  • Thomas and Friends Adventures (coming soon)


Other Railways
DieselBritish Railways
SpencerHiroHiro's FriendsConnorCaitlinStephen's CompetitorsThe Mainland EnginesGatorSamson
AshimaRajivYong BaoVinnieCarlosRaulShaneEtienneFriedaGinaAxelIvan
Spencer's Special CoachesConnor's CoachesCaitlin's CoachesBradford

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