Jack and the Sodor Construction Company (partially lost episodes and production material of cancelled spin-off series; 2002)
Jack and the Sodor Construction Company (more commonly referred to as Jack and the Pack) was a short-lived spin-off of the popular British children's TV show Thomas the Tank Engine and Friends (known as Thomas and Friends at the time) that starred the characters of the pack, introduced in the Thomas and Friends season 6 episodes "Jack Jumps In" and "A Friend In Need". The show was filmed in 2002 but remained unreleased until 4 years later, when Hit Entertainment released the show on various British and American DVDs. However, only 13 of the shows 26 planned episodes were completed before the series was cancelled by Hit Entertainment, who bought the rights to the Thomas brand while production was underway, as they considered it an inferior ripoff of Bob the Builder, a show they had previously created. This cancellation led to a large amount of lost media which has never been released, due to Hit's acquisition of Gullane Entertainment.
Possible Earlier Incarnation
According to an article published in the Guardian, the series's roots could go back even further than the inception of the pack characters themselves. The article, published March 21st, 2001 (more than a year before "Jack Jumps In", the packs introductory episode, first aired in the UK) talks about a Thomas and Friends spin-off starring road vehicles similar to that of Jack and the Pack, but starring existing Thomas characters such as Bertie the bus and Harold the helicopter, instead of completely new characters. It is unknown if this concept got any further than the planning stages, and this article is the only evidence of its existence.
The series was planned to have 26 episodes, similar to that of a typical Thomas season, but only 13 were completed before Hit axed the series. The cancelled episodes were Bossy Byron, Alife Has A Secret, Treasure Hunt, All Work No Play, Grass Is Greener, Jack & The Quack, The Importance Of Being Patrick, Isobella Gets Steamed, Kelly's Heroes, Pop Goes The Diesel, Jack's Snow Rescue, Safety First and No Dozer Is An Island.
It's unknown if production had actually begun on these episodes before they were cancelled and the only details that are known about these episodes are their plot synopses, which all but two episodes are publicly known. The only production details for these episodes are the writers for seven of the episodes, With Paul Larson being the writer for "Pop Goes the Diesel" and "Bossy Byron", Paul Dawson being the writer for "Jack's Snow Rescue", Robin Rigby being the writer for "Treasure Hunt" and "Safety First", Will Ing being the writer for "All Work, No Play", and Brian Trueman being the writer for "No Dozer is an Island". Interestingly, based on some of the cancelled episodes plot synopses, it seems as though certain Thomas and Friends episodes were based on these cancelled episodes, such as "Pop Goes the Diesel" (not to be confused with the Thomas The Tank Engine episode of the same name) being reworked into the episode "Thomas to the Rescue" in season eight of Thomas & Friends, and "Grass is Greener" being reworked into the episode "The Switch" in season seventeen. Oddly enough, Trackmaster merchandise was made and released based off the cancelled episode "Jack's Snow Rescue", which were repaints of the construction vehicles but with snow details to match the episode.
In September 2022, full plot descriptions for 11 of the 13 canceled episodes were found, along with full scripts for two of them. The plots and scripts were found by Ben Gosling, CTFEologist and epiclafiteau on Twitter, who all helped repair corrupted files of the plots/scripts sent by people who worked on the show. 
|1||Bossy Byron||Found||Only a screenplay (dated May 30th, 2002) was written.|
|2||Alife Has Kittens||Found||Completed and first released in the UK in October 2006.|
|3||Jack Owns Up||Found||Completed and first released in the US in August 2006.|
|4||Alfie Has A secret||Found||Only a plot outline (dated April 24th, 2002) was written.|
|5||Treasure Hunt||Found||Also known as "The Sodor Treasure Hunt", only a plot outline was written.|
|6||Who's The Boss||Found||Completed and first released in the US in August 2006.|
|7||Oliversaurus||Found||Completed and first released in the US in August 2006.|
|8||All Work, No Play||Found||Only a screenplay was written.|
|9||Grass Is Greener||Found||Also known as "Jack and Alfie Swap", only a plot outline was written.|
|10||Mud Glorious Mud||Found||Completed and first released in the UK in October 2006.|
|11||Jack & The Quack||Found||Only a screenplay was written.|
|12||The Importance Of Being Patrick||Found||Only a plot outline was written.|
|13||Buster 1 Moles 0||Found||Completed and first released in the UK in October 2006.|
|14||Tortoise And The Hare||Found||Completed and first released in the UK in October 2006.|
|15||Scaredy, Scaredy||Found||Completed and first released in the US in August 2006.|
|16||Isobella Gets Steamed||Found||Only a plot outline was written.|
|17||Kelly's Heroes||Found||Only a screenplay (dated February 26th, 2002) was written.|
|18||Pop Goes The Diesel||Found||Only a screenplay (dated March 22nd, 2002) was written (later remade into Thomas to the Rescue).|
|19||Jack's Snow Rescue||Found||Only a plot outline was written.|
|20||Five Easy Pieces||Found||Completed and first released in the US in August 2006.|
|21||Nelson Gets Carried Away||Found||Completed and first released in the UK in October 2006.|
|22||Byron Saves The Day||Found||Completed and first released in the US in August 2006.|
|23||Another Fine Mess||Found||Completed and first released in the UK in October 2006.|
|24||The Lightning Tree||Found||Completed and first released in the UK in October 2006.|
|25||Safety First||Existence Unconfirmed||Unknown if anything was completed.|
|26||No Dozer Is An Island||Existence Unconfirmed||Unknown if anything was completed.|
Along with the scrapped episodes and possible earlier variation, the show also had a dropped two characters, Trevor and Nigel, the former of which appeared in various episodes of Thomas & Friends in the past and was originally going to have a much larger role in the series but was reduced to a cameo in the episode Mud Glorious Mud, the latter was a lorry painted cream and green with the number 21 on his side. Nigel has reportedly dropped due to none of the episodes scripts had him involved in any way, and the only evidence of his existence is a piece of concept art. A large-scale model of Trevor was built for the series, but since his role was cut, it was used for a learning segment in Thomas & The Tuba and Henry and the Flagpole. No confirmation as to whether or not a model for Nigel exist has resurfaced, and if one does, no photos have resurfaced to prove it. There is still a chance all of this media could still get released, if any of it exists, due to the rising popularity of the pack characters, after Jack made his return to Thomas and Friends in the straight-to-DVD movie King of the Railway, Alfie and Oliver's return in the straight to DVD movie Sodor's Legend of the Lost Treasure, and Max and Monty's return in season 20.
According to Mike O'Donnell on YouTube, he and Junior Campbell had originally composed the soundtrack for this spinoff series back in 2002. However, when the series was released on DVD, the soundtrack was completely redone by Robert Hartshorne. To this day, Mike and Junior's soundtrack for the spin-off remains lost and has not surfaced since.
Thomas & Friends
- Thomas & Friends: All Engines Go (partially found test animation of reboot of British children TV series; 2019)
- Thomas & Friends: Day of the Diesels (lost original cut of direct-to-DVD film; existence unconfirmed; 2011)
- Thomas & Friends "Jack Jumps In" (found Alec Baldwin narration of British children's TV series episode; 2002)
- Thomas & Friends "Series 7" (partially found original music of British children's TV series American dub; mid-2000s)
- Thomas & Friends "Series 12" (partially found Pierce Brosnan narrations of British children's animated series; 2008)
Thomas the Tank Engine
- Thomas the Tank Engine (lost pilot episode of unproduced 2D animated adaptation of "The Railway Series" books; 1976)
- Thomas the Tank Engine "Down the Mine" (partially found pitch pilot version of British children's TV series episode; 1983)
- Thomas the Tank Engine "The Missing Coach" (partially found footage from cancelled British children's TV series episode; 1986)
- Thomas the Tank Engine "Season 3" (found original Michael Angelis narrations of British children's TV series episodes; 1991)
- Thomas the Tank Engine "Season 4" (found pre-recorded version of British children's TV series episodes; 1994)
- Thomas the Tank Engine & Friends (partially lost deleted scenes of British children's TV series; 1984-2021)
- The Adventures of Thomas (partially found production material of cancelled "Thomas the Tank Engine" live-action film; early-mid 2010s)
- Barry the Rescue Engine (lost production material of cancelled "The Railway Series" book; 1980s)
- Storytime with Thomas (partially found Fox Family series; 1999-2000)
- The Thomas & Friends Institute of Innovation (partially found informational short film; 2013-2014)
- Thomas and the Magic Railroad (found deleted scenes of children's fantasy adventure film; 2000)
- Thomas and the Magic Railroad (lost test footage of 3.5" character models for British children's TV series; 1995)
- Thomas and the U.K. Trip & Thomas Number 1 (found Japanese "Thomas the Tank Engine" crossover TV special and music video; 1991)
- Thomas the Tank Engine (found original illustrated edition of book; 1946)
- Thomas the Tank Engine & Friends (found build of cancelled NES port of educational game; 1993)
- Thomas the Tank Engine and Friends (lost build of cancelled PlayStation educational game; 1999)
- The Three Railway Engines (lost live BBC broadcast adaptation of "The Railway Series" books; 1953)
- The Three Railway Engines (found original edition of book; 1945)
- Page talking about the possible earlier incarnation.
- Page talking about the cancelled episodes and George's removal.