"Despite becoming the most popular character in The Railway Series, Thomas did not actually feature in the first book, The Three Railway Engines (namely Edward, Henry, and Gordon).
"Thomas was described in the opening to "Thomas and Gordon", the first story in book two, Thomas the Tank Engine, as: a tank engine who lived at a Big Station. He had six small wheels, a short stumpy funnel, a short stumpy boiler and a short stumpy dome.
"He was a fussy little engine, always pulling coaches about. —from the story "Thomas and Gordon" in Thomas the Tank Engine.
"Thomas was used initially as a station pilot engine in the first three stories in book 2, but longed for more important jobs such as pulling the express train like Gordon; his inexperience prevented this. In the fourth story, Thomas & the Breakdown Train, Thomas rescues James and is rewarded with his own branch line. He has remained in charge of the Ffarquhar branch ever since, with his two coaches Annie and Clarabel, and help from Percy and Toby. Thomas is generally depicted with a cheeky and even self-important personality. He believes that he should be more respected by the others, and he gets annoyed when he does not receive this respect. However, Percy and Toby are more than capable of standing up to him, and Annie and Clarabel often rebuke him."
"In 1979, the British writer/producer Britt Allcroft came across the books, and arranged a deal to bring the stories to life as Thomas the Tank Engine and Friends (later simplified to Thomas and Friends). The programme became an award-winning hit around the world, with a vast range of spin-off commercial products."
"HiT Entertainment, which acquired Gullane Entertainment, formerly the Britt Allcroft Company, licenses 'Day out with Thomas'. On February 1, 2012, HIT Entertainment became a wholly owned subsidiary of Mattel, managed under its Fisher-Price unit."
Thomas The Tank Engine™ first appeared in the Lionel yard in 1999 as uncataloged #21918 Thomas Circus Play Set, followed by #21925 Thomas Tank Engine Island of Sodor Set-1999 Volume 2. Included in this set was Thomas, Annie, Clarabel and Harold the Helicopter, a station house, a 27" x 36" oval of O-27 track and a power pack/controller.
That catalog had for sale three separate sale items: Troublesome Truck I and II and "Percy, the small engine, (who) is a young happy chap who is content with puffing around the yard. He doesn't care much for seeking out great adventure in the world outside the yard, but is always happy to oblige his fellow engine friends."
#18722 Percy featured a DC can motor, metal wheels, stamped metal chassis, molded body, non-operating coupler, Tire-Traction™ and a three position reversing unit. The locomotive could be locked into a certain mode of operation by throwing the switch located inside Percy™ cab after removing the roof and had a MSRP of $99.95
Most likely to promote the new Lionel FasTrack first shown in the 2003 Vol 1 catalog, an upgraded Thomas™ set #31956 was issued in the 2004 Vol 2 catalog. This set included Thomas the Tank Engine™ with three interchangeable faces, moving eyes, electronic whistle, operating coupler on the rear of the locomotive, maintenance-free motor, traction tire, removable roof and Annie, Clarabel, three play figures and FasTrack measuring 40" x 60".
Because he was such an obliging fellow, Percy went to the same Botulinum toxin doctor as Thomas and got a similar facelift in the 2005 Vol 2 catalog as #18733 with a MSRP of $119.99
It featured a transformer controlled forward, neutral and reverse operation; powerful maintenance-free motor; operating whistle; operating coupler on rear of locomotive; removable roof and moving eyes and a set of three removable faces (on a botox enhanced mug of course J). Unlike his compadrie, he does not have traction tires.
#18722 (TOP) had a longer fixed non-operational coupler; a screw in the center of the cab and one on/off switch, can motor with gears and small rollers. # 18733 (BOTTOM) had an operational coupler, no screw hole and a pair of switches (one each for the whistle and reverse unit on/off) along with a longer set of rollers. You can see that the chassis was connected to the shells in different places.
Although shown here for convenience sake for web browsing top to bottom, the box for 18722 (TOP) is of similar size and shape to a regular 6464 style boxcar (12"L x 5 1/8"D x 3"H) and the box for 18733 (BOTTOM) is of similar size of a modern motorized unit (9 ½"L x 5 ¼"D x 4 3/8"H)
The Greenberg's Pocket Price Guide 1901-2012 values the earlier, lighter version #18722 at $170 and heavier, enhanced version #18733 at $120.