Thomas is a tank engine and the main character of the long-running and successful TV series Thomas and Friends (titled Thomas the Tank Engine and Friends before 2003), a TV series based on The Railway Series by the late Rev. Wilbert Awdry. He is a tank engine who lives in a big station in the Island of Sodor. He's a blue, cheeky little engine with 6 small wheels, a short stumpy funnel, a short stumpy boiler and a short stumpy dome.
In terms of the SMG4 universe, Thomas has made a few cameo appearances. He made a cameo in War of the fat italians 2014 and The SMG4 QNA as a flying engine with a Eggman face saying PINGAS. He also made a quick cameo in The 2spooky Story. His theme was played when the train was gonna sqaush Peach in Toadworth's How to Princess. His most notable face, the :O Face was also featured in the same blooper, as well as the front of the Teletubmarine in the first part of SMG4'n pals. He appeared in Shy Guy Showdown with an Eggman face with rainbows on the back, and in SMG4: Mario's Train Trip to get Mario, SMG4 and Toad to Uniderpal Studios.