Jack is a friendly and enthusiastic front loader.
When Jack first arrived on Sodor, he worked with the Pack to clear room for railway lines. Jack did well with Alfie - that is, until he tried to take some stone up a ledge but lost balance and tipped over. Jack learned his lesson, and redeemed himself by holding up a collapsing bridge until Thomas had passed over, at the cost of damaging his arms. Jack has since become part of the Pack.
When Jack was being careless at the warehouse, he knocked over some slate, but he didn't want to be send back to the yards and left the mess not knowing that Ned was blamed for it and was being send back to the yards, until he heard from Alfie and admited that he broke the slate and was sent back to the yards.
He, along with the rest of the Pack, helped with the restoration of Great Waterton and worked with Alfie to construct a bandstand there. Jack also helped with the restoration of Ulfstead Castle and later saved Stephen and Thomas after the tracks they were on collapsed.
He also helped build the Harwick Branch Line, along with Alfie, Oliver, Max and Monty, and later attended the branch line's opening ceremony.
A magazine fact file states that he now works at the Sodor Slate Quarry.
Jack is brave and will not take any hassle, as seen whenever he stands up to Monty and Max when they are bullying him and Alfie. He is also kind and caring.
It is unclear what type of vehicle Jack is based on, but between the sixth and twelfth season he seemed to resemble a Nuffield tractor with an added front loader.
Since King of the Railway, Jack's basis has closely resembled an International 454 tractor. Because of this, his face shape has changed dramatically from round to rectangular.
Jack is painted red with the top half of his cab and his wheels painted cream. He has the number 11 painted in white on his sides. From King of the Railway onwards, the top half of his cab is painted grey, his back wheels are painted grey and his front wheels are painted red.
- Steven Kynman (UK; King of the Railway onwards)
- David Menkin (US; King of the Railway onwards)
- Tim Kreuer (Germany; King of the Railway only)
- Naomi Shindō (Japan; sixth season only)
- Hideki Nakanishi (Japan; The Great Discovery - twelfth season)
- Keiko Nemoto (Japan; King of the Railway onwards)
- Artur Pontek (Poland)
- Paul Disbergen (The Netherlands)
- Scott Maurstad (Norway; King of the Railway only)
- Nacho Rodríguez (Latin America; King of the Railway onwards)
- Mariano García (Spain)
- In some promotional sketches of the Pack, Jack is seen with a backhoe arm and bucket. According to an SiF interview with Chris Lloyd, the arm was built, but was too problematic as it was hard to store all of the radio gear inside the model. An interview with Phil Fehrle gives a very different reason: "...if a story required Jack to be digging (using his back-hoe) and interacting with another character working at the same time, his face would be facing away from the action. For story purposes, it was important to feature the faces as much as possible; thus, the backhoe was removed."
- Jack has had a few modifications in the television series:
- King of the Railway:
- He gained hydraulics.
- His exhaust pipe became taller.
- He decreased in size.
- His face changed from round to square like his basis.
- His rear wheel cover was moved back.
- The colour of his alloys also changed from cream to grey; like Alfie.
- King of the Railway:
- Nathan Clarke did an audio sample for Jack on his DAA Management Page
- A semi-complete face mask of Jack was preserved by the Top Props preservation group.
- "Spot on, Jack! You'd make a mother proud!"
- "And a tank engine grateful!"
- Miss Jenny and Thomas praising Jack, A Friend in Need, sixth season
- ERTL (discontinued)
- Wooden Railway (reintroduced 2013)
- Take Along (discontinued)
- Take-n-Play (reintroduced 2013)
- TrackMaster (motorised and un-motorised)
- My Thomas Story Library (discontinued)
- Thomas Engine Collection Series (discontinued)
- Mini Die Cast Collection (discontinued)
- Thomas Town (discontinued)
- Wind-up (Japan only)
- Pocket Fantasy (discontinued)
- Nakayoshi (discontinued)
- Thomas and Friends Adventures (coming soon)