P.T. Boomer is the main also referred to as Boomer, was supposed to be the main villain alongside Diesel 10 in Thomas and the Magic Railroad, but was cut from the film as test audiences complained that he was too scary for a younger audience. However, he can be seen in a shot, such as the final chase scene as a black cable box used on Diesel 10's cab, and also appeared in the trailers. He was portrayed by the late Canadian actor, Doug Lennox.
Boomer is an opportunist, who has drifted from situation to situation, making money wherever he can - usually out of others misfortunes. He is an emotionally muddy man who is obsessed with cleanliness and order. Now he is out of opportunities, except one - to return to Shining Time with only himself, his motorcycle, a lifelong grudge and a thirst for revenge.
P.T. Boomer was jealous of the relationship that Burnett Stone had with Tasha and bullied Burnett into allowing him to take Lady for a run. After crashing her, he left Shining Time while Burnett spent years trying to restore her, to no avail. Boomer is described in the script as being "a drifter through choice, not circumstance". He returns forty years later now a bitter and dark character bent on getting rid of Lady.
Boomer is the reason behind Mutt's unease and the reason for bringing Lily to Shining Time rather than letting her go on to Muffle Mountain. Boomer spends much of his time throughout the film arguing with Burnett Stone and Billy Twofeathers and digging into the mountain looking for Lady.
He has no (said) ownership or connections with Diesel 10, not even meeting him until the film's climactic chase scene, other than their shared desire to destroy Lady and Sodor. He does not believe in magic and when he finds Thomas in the real world on Muffle Mountain, he believes that he is just a huge toy. Thomas is the reason why Boomer ends up on Sodor: he discovers the entrance to the Magic Railroad after Thomas rolls down the mountain (due to Boomer using explosives to destroy the ledge where Thomas is stuck on) and falls through it. When Thomas and Lady arrive back on Sodor, Diesel 10 arrives, just as Boomer flies through the magic buffers. Landing on Diesel 10's roof, he declares that he is after Lady as well, to which the former declares "that makes two of us!" Boomer spends the chase throwing taunts at Burnett, to which Burnett declares that "the magic [he] refuse[s] to believe in will get the better of [him]".
He and Diesel 10 meet their fates during the chase scene when they plunge off the viaduct into a barge filled with sludge. Boomer spits water out of his mouth and angrily glares into the camera.