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“It's a mystery. I love a mystery! Imagine us as special agents!”

The Case of the Puzzling Parts is the twenty-third episode of the twenty-second series.


Sidney has a flatbed with some parts that are needed, but he forgets why the parts are needed. Paxton decides that he and Sidney should be special agents to find out what they are for, they found out from Thomas that the parts are for a diesel engine. While they are searching for more clues to find, Sidney starts to have a few problems with himself, and Paxton points out that he has a wonky horn, a broken lamp and a faulty buffer, and he is coughing up black smoke. Both diesels realise that the parts are for Sidney himself.





US and CAN

  • Joseph May as Thomas
  • William Hope as Whiff
  • Keith Wickham as Skarloey
  • Steven Kynman as Paxton and Dart
  • Bob Golding as Sidney
  • Tim Whitnall as Reg


  • Going by production order, this is the twenty-fourth episode of the twenty-second series.
  • Paxton breaks the fourth wall once again in this episode, as does Sidney.
  • This episode marks the last and only of a few things:
    • The last time Skarloey is seen without the brass ring around his funnel.
    • Whiff, Scruff, Dart and Luke's only appearances in the twenty-second series, as well as Sidney and Skarloey's only speaking roles in the twenty-second series.
    • Whiff and Scruff's last appearances, though Whiff is mentioned in Thomas & Friends: All Engines Go!, and is likely to appear.
    • The last appearance of Whiff's Waste Dump, although it was mentioned in the next series and in the reboot.
  • On the Nick Jr. US airing of this episode, it was paired with Outback Thomas.


  • When Thomas backs away from Sidney, he makes no puffing sounds and Paxton's engine does not make a sound when he reverses alongside Sidney.
  • Sidney and Paxton travel on narrow gauge track in the tunnel at the Blue Mountain Quarry despite being standard gauge engines.
  • Throughout the episode, Sidney's wheels move slower than the speed he is travelling at.
  • Nick Jr.'s captions misspell Sidney as Sydney throughout the episode.

In Other Languages

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Language Title
Arabic قضية قطع الغيار
Brazilian Portuguese O Caso das Peças Intrigantes
Czech Případ Tajemných Součástek
Danish Sagen om de mystiske dele
Dutch De Zaak van de Onbekende Onderdelen
Finnish Varoosien Arvoitus
German Auf Spurensuche
Greek Το Μυστήριο των ανταλλακτικών
Hebrew תעלומת החלפים המסתוריים
Hungarian A fura részek ügye
Italian Il Caso dei Pezzi Misteriosi
Japanese ぶひんのなぞをさぐれ!
Korean 수수께끼 부품의 주인은 누구?
Latin American Spanish El Caso de las Piezas Misteriosas
Norwegian Saken om de Savnede Delene
Polish Sprawa Tajemniczych Części
Portuguese O Caso das Peças Misteriosas
Russian Загадочное дело
Serbian Slučaj Zagonetnih Dijelova
Spanish El Caso de las Piezas Desconcertantes
Swedish Mysteriet med de förbryllande delarna
Turkish Gizemli Parçalar Vakası

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