- "You're barkin' up the wrong branch line there, buddy boy!"
- ―Lexi, Journey Beyond Sodor
Lexi is a boisterous cab-forward engine.
When Thomas travels to the Mainland, he befriends the experimental engines: Lexi, Theo, and Merlin. Thomas encounters Lexi and Theo in an empty yard, where he is warmly welcomed and refilled with coal. Later, Lexi, along with the other experimentals, help Thomas rescue James, who had been trapped in the Steelworks.
Afterwards, Thomas encourages Lexi (along with Theo and Merlin) to stay with Frankie and Hurricane and call the Steelworks their new home.
Lexi likes to experiment with how she presents herself, often trying out different voices and how she phrases her expressions just to see which one she thinks works best. Another “experimental engine”, she is “cab forward”, even though she is convinced this makes her "an un-useful engine."
Lexi is based on the North Pacific Coast Railroad Cab-Forward 4-4-0 No. 21 "Thomas-Stetson", a rebuild of NPCRR #5 which was dismantled by 1897. An innovative engine built by Bill Thomas, it is considered the first cab-forward locomotive and was one of the first oil burners, as well as the first locomotive to use a marine boiler. The engine had insufficient adhesion weight and its oil burners were prone to damage due their proximity to its water tubes, and was unpopular with crews, its unusual appearance earning it the nickname "The Freak". #21 was scrapped in 1905.
Lexi is painted light turquoise with a gold cowcatcher. Her front windows have gold lining, and her side windows have copper lining. Her main body is covered in rust. She has brass nameplates fixated on each side of her cab and the initials "N.P.C.R.R" painted on her rear oil tank.
- 2017 - Journey Beyond Sodor
She may appear in Season 22.
- Lexi has received several modifications compared to her basis:
- Lexi has been modified to accommodate a face, as a lamp would actually be were her face is. Her lamp has also been moved to her added footplate.
- She has been modified for working on British railways with the addition of buffers and a screw-link coupling on her tender, as well as brake-pipes on her front and back.
- She has been regauged from 3ft gauge to standard gauge.
- Lexi speaks with a Scottish accent and imitates many other dialects, despite being based on an American engine.
- Lexi's tender wheels are actually reused from Marion's wheels, and her bell is reused from Belle's bell.
- Lexi shares the same whistle sound as the Rainbow Sun and Carlos.