Seeing is Believing

"How come I didn't see the invisible engine?" "Probably because he's invisible, eh?"

- Percy and Nia

Seeing is Believing is the thirteenth episode of the twenty-second series.

Plot
Merlin is visiting Sodor from the Mainland to deliver steel. He is excited about visiting Sodor, as he will be seeing Thomas and tries to make himself invisible, then Thomas pretends to try and find Merlin somewhere and pretends to think he can't see him anywhere until Merlin surprises Thomas and then he's so happy that he and Merin and reunited together again, then Salty warns Rebecca that there's an invisible engine in the yard today but to Rebecca's surprise she thinks Merlin can't be invisible and Thomas tells her Merlin is an experimental engine who thinks nobody can see him but they know it's only pretend.

Merlin later comes up alongside Thomas and surprises him again. While doing so, Merlin hears a whistle in the distance and is surprised by Trevor, having never seen a traction engine before. Thomas then introduces Trevor to Merlin, who also tries to convince Trevor about his invisibility.

All of the engines at Tidmouth Sheds begin talking about Merlin, though Percy is upset about not being able to see him. He dreams about trying to see Merlin, but cannot because he is invisible. Percy tries looking for him the next day and soon hears a whistle that he believes is Merlin's. Although Merlin comes up beside Percy, Percy does not know that he is the engine and rushes off to tell Thomas about how he has heard his whistle. This makes Percy very happy by how he thinks he has seen the invisible engine.

Characters

 * Thomas
 * Gordon
 * James
 * Percy
 * Emily
 * Merlin
 * Nia
 * Rebecca
 * Salty
 * Trevor
 * Cranky
 * Carly
 * Annie and Clarabel
 * Porter
 * Diesel
 * Paxton
 * Owen
 * Reg
 * Big Mickey
 * Jem Cole
 * The Lady with the Big Hat
 * Farmer Finney
 * Cyril the Fogman
 * Farmer McColl
 * Willie
 * Henry
 * Theo
 * Lexi

Locations

 * Island of Sodor
 * Vicarstown Bridge
 * Brendam Docks
 * Sodor Shipping Company
 * The Sheep Field
 * Tidmouth Sheds
 * Wellsworth
 * Crocks Scrap Yard
 * Blue Mountain Quarry
 * McColl Farm
 * The Mainland
 * The Steelworks

UK

 * John Hasler as Thomas
 * Keith Wickham as Gordon and Salty
 * Rob Rackstraw as James
 * Nigel Pilkington as Percy, Trevor and Merlin in Percy's fantasy
 * Teresa Gallagher as Emily, Annie and Clarabel
 * Hugh Bonneville as Merlin
 * Yvonne Grundy as Nia
 * Rachael Miller as Rebecca
 * Matt Wilkinson as Cranky
 * Lucy Montgomery as Carly

US and CAN

 * Joseph May as Thomas
 * Kerry Shale as Gordon
 * Rob Rackstraw as James
 * Christopher Ragland as Percy and Trevor
 * Jules de Jongh as Emily
 * Hugh Bonneville as Merlin
 * Yvonne Grundy as Nia
 * Rachael Miller as Rebecca
 * Keith Wickham as Salty
 * Teresa Gallagher as Annie and Clarabel
 * Glenn Wrage as Cranky
 * Lucy Montgomery as Carly
 * Nigel Pilkington as Merlin in Percy's fantasy

Trivia

 * Going by production order, this is the eighteenth episode of the twenty-second series.
 * This episode marks:
 * The last episode written by Andrew Brenner, the next series being his last as head writer despite not writing any episodes. David Stoten would take over as head writer beginning with the twenty-third series special episode, Steam Team to the Rescue.
 * Merlin's only appearance in an episode and his only appearance in the twenty-second series.
 * Trevor's only speaking role in the twenty-second series.
 * Merlin and Trevor's last appearances.
 * The only episode in which Reg appears but does not speak.
 * Trevor reuses Vinnie's whistle sound in this episode.
 * At the beginning of the Latin American Spanish and Brazilian Portuguese dubs, stock footage from the twenty-second series episode Forever and Ever is used.
 * The episode's plot is almost similar to the eleventh series episode, Thomas and the Spaceship.
 * On the Nickelodeon and Nick Jr. US airings of this episode, it was paired with Thomas and the Dragon.

Goofs

 * When Thomas is talking to Rebecca at the docks, some wooden planks are clipping through Carly's rails.
 * Nigel Pilkington was not credited for voicing Merlin in Percy's fantasy scene in the US dub.
 * Thomas does not have a number when Merlin is talking to Rebecca.
 * Because of stock footage that was used in the Latin American Spanish and Brazilian Portuguese dubs, Henry is seen at Tidmouth Sheds instead of Rebecca.
 * In the opening for the episode, the wooden fence closest to the Walney Channel is floating off the ground.

UK/AUS

 * Monkey Trouble!

GER

 * Big World! Big Adventures! - Adventures In Sodor