- “Definitely a coloratura.”
- ―Gordon after hearing Allicia Botti scream
Thomas, Percy and the Squeak is the twenty-first episode of the sixth series.
Allicia Botti, a famous opera singer, is coming to Sodor for a concert and the engines are wondering who will take her to the venue at the castle, a job that Gordon states Percy will not be chosen for as he is very dirty. Come the following day, the Fat Controller choses Thomas and tells him to be squeaky clean.
Thomas goes to the washdown where Percy is waiting to be cleaned. However, Thomas insists that he must go next as he has an important job. Percy sets off, still dirty, to collect some coaches for his guaranteed connection. Once Thomas and his coaches are cleaned and prepare to set off, however, they hear a squeak. His crew assume that Annie and Clarabel's wheels are the cause of this, so they oil them. But, once on the move again, the squeak continues on, making Thomas concerned.
At Brendam, Thomas pulls up to collect Allicia Botti and the Fat Controller opens one of Clarabel's doors. However, there is a mouse inside, which causes Allicia Botti to scream in horror; she screams so loudly that windows shatter all around Brendam. Allicia Botti is cross and refuses to ride onboard Clarabel, much to the embarrassment of Thomas and the Fat Controller. Because of this, Thomas does not feel important at all. Just then, Percy arrives back from his guaranteed connection and Allicia Botti considers him as a proper engine because of his dirty appearance and decides to ride in one of his coaches instead.
Later, Thomas is back at the washdown when Percy arrives. This time, he lets Percy go next for his wash. That night, whilst Allicia Botti is performing her concert at the castle, Thomas and Percy are at Tidmouth Sheds where the mouse, whom Thomas named "Allicia," now lives.
- Sir Topham Hatt
- Allicia Botti
- Annie and Clarabel (do not speak)
- Henry (cameo)
- Big Mickey (cameo)
- Stephen Hatt (cameo)
- Mrs. Kyndley (cameo)
- Refreshment Lady (cameo)
- Nancy (cameo)
- Farmer Trotter (cameo)
- The Storyteller (cameo)
- The Lighthouse Keeper (cameo)
- The Special Visitor (cameo)
- The Dockyard Manager (cameo)
- Edward (stock footage cameo)
- Toby (stock footage cameo)
- Bridget Hatt (stock footage cameo)
- Brendam Docks
- Tidmouth Bay
- Tidmouth Sheds
- Shunting Yards
- The Lighthouse
- Tidmouth Beach
- The Washdown
- The Works
- The Windmill (stock footage)
- Stock footage from Percy's Chocolate Crunch is used, as is edited stock footage from Scaredy Engines. This is noticeable as, on the left of the scene, what appear to be jack-o-lanterns can be seen next to where the fireworks would have been in that episode.
- Allicia Botti's scream was used from a woman's scream from the 1996 film Independence Day.
- The sound effect for the mouse is often used as a squeaky door. It was particually used in "The Simpsons" episode, "Please Homer, Don't Hammer 'Em."
- A script dub of the episode was done in the Japanese show "Ponkids 21," with Leo Morimoto reprising his role as the narrator, with members of REAL BLOOD doing the character voices. Leo later voiced James in another take.
- The squeak is different at the end on the Bumper Party Collection! DVD.
- At the end of the episode, the mouse squeaks once in the UK version, but in the US version, it squeaked twice.
- In the last close-up of Allicia Botti screaming, there is an animation effect for her uvula seen in her mouth.
- Due to scenes on one particular set across the season being filmed in one go, the scene at Knapford in this episode looks pretty similar to the first scene at Knapford in Edward the Very Useful Engine. The same people are boarding the same trains, the same engines are in the same positions, and the same posters are up.
- At the beginning a poster of Allicia Botti is visible; it says she is performing at the castle tonight, but she was performing the next night.
- When Thomas arrives at the docks, his steam platform is visible.
- Gordon's front and rear bogie are severely derailed in the last scene of Thomas and Percy at the washdown.
- When Percy arrives at Brendam, his steam platform is visible and some of the steam from his funnel disappears, indicating a film cut.
- Allicia the mouse is missing her forepaws when she is inside Clarabel.