Double Teething Troubles

"Toothache? He's got teething troubles. That means he's new and is causing some problems. In his case it's in his cooling system."

- Duck explaining teething troubles to the twins

Double Teething Troubles is the twelfth episode of the fifth season.

Plot
Bill and Ben argue over who has rights to some trucks nearby, and, despite BoCo's warnings, derail each other at the points. The Fat Controller decides to send a Diesel to help them, but the Diesel, Derek, is new and has problems with his cooling system, as seen after he breaks down on Gordon's Hill, prompting BoCo to rescue him. The news soon spreads, and Percy, who misunderstands Thomas when he mentions Derek has teething troubles, tells the horrified twins the Diesel has a toothache. Duck tells the twins that "teething troubles" means that Derek is new and breaks down often, making the twins even more nervous. The next day, Derek arrives at the Clay Pits and helps the twins with a long train of China Clay trucks. However, Derek's engine overheats, and he stops. Bill and Ben pull him and the trucks and Derek is sent to the works. Bill and Ben apologize to BoCo for being rude and they and Duck talk about teething troubles all night long.

Characters

 * Thomas
 * Percy
 * Duck
 * Bill and Ben
 * BoCo
 * Sir Topham Hatt
 * Derek (not named)
 * S. C. Ruffey (possible cameo)

Locations

 * Brendam
 * Anopha Quarry
 * Gordon's Hill

Trivia

 * Stock footage from Cranky Bugs is used.
 * Teething troubles usually occur while steam engines, Diesels, and other machinery are operating for the first time after being constructed or restored to working order.
 * S. C. Ruffey's face appears on a truck. It is unknown if this was simply a mistake on the part of the model makers, or if it was an intentional appearance of the character.
 * This episode marks BoCo's last speaking role to date.
 * Despite his appearance in the episode, Percy does not appear in the nameboard sequence at the end of the episode in Japan.

Goofs

 * It is said that Bill and Ben heard an unfamiliar whistle (Derek's), but Diesels have horns.
 * A grey cord can be seen in Bill's cab when he's in the shed at the end.
 * In the first close-up of BoCo, his front wheels are derailed.
 * During the first night scene in the shed, a grey cord can be seen stretching along Bill's side.
 * When Percy leaves Thomas, Thomas' eyes are wonky.
 * The train next to Thomas passes him twice.
 * A rare picture from The Ultimate Diesel Guide shows Derek smiling after he overheats.
 * BoCo has Daisy's fourth season horn sound.

Quotes

 * Bill: "That's my line of trucks!"
 * Ben: "It's not. It's mine! Yours is over there!"
 * Bill: "'Smine."
 * Ben: "'Snot."
 * Bill: "'Smine!"
 * Ben: "'Snot!"
 * BoCo: "Stop bickering you two or the only thing you'll have left to share is..." (Bill and Ben race towards the trucks but crash into each other at the points) "...trouble."
 * Bill: "Silly!"
 * Ben: "Silly yourself!"


 * Percy: "Hey you two! This new diesel's got toothache. Good luck!"
 * Bill: "Why does Percy want to wish us good luck?"
 * Ben: "Because he'll know we'll need it, a Diesel with a toothache must be the worst diesel of all!"
 * Derek: "I'm overheating again!"
 * Bill: "Oh pah!"