- “Safety first, means you don't rush in where you don't belong!”
- ―Miss Jenny scolding Jack after his accident.
Jack Jumps In is the seventh episode of the sixth season.
Thomas is sent by The Fat Controller to pick up a special from Jenny Packard. He arrives to see that his special is an eager front-loader named Jack to help The Pack clear ground for railway lines at the quarry. Thomas drops him off there and Jack looks for someone to help. He asks Oliver the Excavator and Byron the Bulldozer, whom both decline the need for help and Byron tells Jack to try Kelly the Crane. When Jack introduces himself, a lorry named Isobella rudely tells him to mind her paint work, but apologises and welcomes Jack after Kelly scolds her. They advise Jack to see the Foreman.
The Foreman introduced Jack to his banksman and tells him to work with a small excavator called Alfie. Jack and Alfie were having fun until a dump truck named Max comes along and causes dust to fly over the machines. Jack could see that Thomas was right that he was trouble and Max was about to rush towards him, but stops just in time. Jack becomes furious and whilst refusing to move, scolds Max, who immediately races away in frustration.
Later, the Foreman orders Oliver to move a pile of rocks, but Jack foolishly takes over and picks some of the rock up a hill himself. His banksman tries to stop him, but Jack refuses to do so as he was too eager to help. Unfortunately when he approaches the top of the hill, he loses his balance, overturns and slides sideways downhill.
Once back upright, Miss Jenny is glad Jack was luckily unhurt but was disappointed of his foolishness due to disobeying her "Safety First" rule, meaning no one should jump in where they should not belong. Miss Jenny then thinks he may not be ready to join The Pack but gives Jack another chance to make sure he could do better the following day. After Miss Jenny leaves, Jack feels bad for what he had done, but Isobella, Alfie and Thomas console him, which makes him feel better.
- Miss Jenny
- The Foreman
- Ned (cameo)
- Sir Topham Hatt (mentioned)
- This was the first episode directed by Steve Asquith.
- This was the first episode not directed by David Mitton. However, it is unknown if he was involved in the episode's production.
- This marks the only appearance of The Quarry Construction Site in the television series to date.
- This is the first episode to have widescreen not matted from fullscreen.
- The working title for this episode is "Jack Goes to Work" although it was given that title on the Thomas and the Jet Engine DVD in Australia.
- Alec Baldwin's narration has only been broadcast on the Canadian television stations TVO Kids and Treehouse TV. His narration of the episode was later released on Amazon for digital download and the narration itself was never released on DVD.
- A picture of a deleted scene shows that Ned was originally intended to play a larger role in the episode.
- This is the first episode written by Abi Grant.
- Thomas leaves with the well wagon after delivering Jack, but in the close-up of Jack, the well wagon is still behind him.
- Studio equipment can be seen in the top-right corner when the narrator says, "Byron the bulldozer was shoving rock and rubble with his giant blade."
- When the Foreman introduces himself to Jack, he has a moustache, red hair and a hat. When he says "Oliver, move this rock!" he has a hard hat and no moustache.
- When Jack introduces himself to Alfie, Alfie's front-left tyre is flat.
- In some shots, a wire is visible under Alfie's hydraulic arm.
- When Isobella yells "No!" when Jack goes up the hill, wires can be seen in her cab.
- Before Jack barrel-rolls down the slope, his two left wheels have much more sand on them and the tyres now because of this appear grey.
- When Max spins around, the turntable that makes him spin is visible.
- When Thomas first meets Jack, he makes diesel noises when he stops.
- In Michael Angelis' American narration, the term 'lorry' is still used.
- Miss Jenny: Spot on, Thomas! You'd make a mother proud!
- Thomas: Thanks, Miss Jenny. Is this my special?
- Miss Jenny: Very special.
- Jack: I'm Jack, the front loader. I can load, unload and carry lots of things.
- Thomas: I can haul and shunt.
- Miss Jenny: And I can get you two chatterboxes off to the quarry.
- Thomas: Is this your first job on the quarry?
- Jack: It's my first job on the Island!
- Thomas: Look out for Max! He's trouble!
- Jack: I'm Jack, can I help?
- Oliver the excavator: Oh my. No. Help Byron.
- (Jack finds Byron the bulldozer moving rocks)
- Jack: I'm Jack, can I help?
- Byron: I don't need help. Try Kelly the crane.
- Jack: I'm Jack!
- Isobella: Mind my paint!
- Kelly: Isobella!
- Isobella: Sorry. Welcome to The Pack.
- Kelly: And if you want to help...
- Isobella: See the Foreman. He's in charge.
- (The Foreman introduces Jack to his banksman)
- Banksman: I'm here to help you work safely.
- Foreman: No speeding and no horseplay, now go and help Alfie.
- Jack: Yes, sir!
- Banksman: Remember: Safety first!
- Jack: I'm Jack, I'm here to help.
- Alfie: More help means more dirt, more dirt means more fun. I'm Alfie.
- (While Jack and Alfie are at work, a dump truck named Max races by)
- Alfie: MAX!
- Jack: So that's Max. Thomas is right. He IS trouble!
- Alfie: (Max almost collides with Jack) Look out, Jack!
- Jack: Stop bullying!
- Max: Can't you take a joke?
- Foreman: Oliver, move this rock!
- Jack: I'll do it! (loads his bucket of the said rock)
- Banksman: Stop!
- (Jack does not stop and makes his way up the hill)
- Isobella: No!
- Jack: Oh no! (overturns and falls downhill) Whoops!
- Miss Jenny: Safety first - means you don't rush in where you don't belong.
- Jack: I'm sorry, Miss Jenny.
- Miss Jenny: Maybe you're not ready for The Pack. We'll see if you can do better tomorrow.
- (Miss Jenny leaves and returns to the yards while Jack is sad; Isobella saw everything)
- Isobella: You're a good front-loader.
- Alfie: ...and a good friend.
- Thomas: Being a good friend is important.
- Take Along (four-pack and film car; both discontinued)
- My Thomas Story Library - Jack (discontinued)