Bill and Ben (T&F)/Behind the Scenes

Gauge 1 models
Bill and Ben's models were custom built with a plastic body shell and used a Märklin locomotive as a donor for the chassis and various parts. They were painted using glossy car body paint and lined with red automotive pinstripe tape with the letters on their saddle tanks were custom cut vinyl stickers.

In the second series, Bill and Ben's nameplates were made to be removable, which was required for the episode, The Diseasel, which centred around the twins playing a trick on BoCo to confuse him with their identical looks. Since the third series their nameplates were replaced with custom printed stickers.

Bill and Ben's wheels were sourced from a gauge 1 locomotive made by Märklin, the BR 80. The buffers were also from the BR 80.

In a behind the scenes picture of Bill's model during the second series reveals that the twins were to have numbers on their smokeboxes above their faces, as they did in The Railway Series. However, they were removed for unknown reasons once filming of The Diseasel began.

During the production of the sixth series Bill and Ben's paint was given a matte finish. In the episode, Buffer Bother, Ben's buffers were temporarily bare brass.

Bill and Ben went through aesthetic changes in the model series. These include:
 * Series 3:
 * Their nameplates were painted on instead of being actual plates.
 * Buffer Bother:
 * Ben gained brass buffers temporarily.
 * Series 7:
 * Ben regained black buffers.

Present Day
After production of the model series wrapped in 2008, most of the models and sets would be put into storage, with some being put on display at Drayton Manor Theme Park. All other models would be logged and referenced in 2009 by HiT Entertainment, from this HiT would decide on which models were to enter storage once again, which would be given to crew members and which to be disposed off. Due to only having one set of models made in gauge 1 scale, Bill and Ben's models would stay under HiT and later Mattel's ownership.

Bill and Ben's models are now currently on display at the Hara Model Railway Museum in Japan.

Faces
Thirteen different facial expressions were sculpted for Bill and Ben, although twelve were used on-screen and one of which his alternative happy face was left unused and used on the Cool Props model replica. The faces were first sculpted in clay and from that resin casts were made using a silicone mould. Some of Bill and Ben's faces were duplicated in case they needed to wear the same facial expression in the same shot. One of Bill and Ben's faces is owned by Twitter user TomsProps. A prototype face for Bill is also owned by Sean O Connor and would be exhibited at the History Of Thomas Event.

CoolProps Replicas
In 2019, faithful replica props were announced by CoolProps in Japan and supposed to be sold to the public. They used the original models located at the Hara Model Railway Museum in Japan for reference.

Fonts
The following fonts were used on Bill and Ben's Gauge 1 models:
 * Benton Bold Condensed
 * Georgia Bold
 * Helvetica
 * Corinthian Medium
 * Arial

CGI models
In 2009, the series introduced Computer-Generated Imagery (CGI) as a replacement for the show's long-standing live-action models. In 2013, Bill and Ben were created in CGI by Arc Productions. The model was "hand-sculpted" in Maya, a 3D animation and modelling software.

Bill and Ben have had modifications throughout the CGI series. These include:
 * Series 17:
 * Their faces became smaller, and were raised slightly higher up.
 * Permanent lamps and taillamps.
 * An additional sandbox was added on the footplate to mount the lamp.
 * An extra wood panel was added to the rear window to accommodate the taillamp.
 * Taller cabs.
 * Brass nameplates.
 * Red lining behind the "SCC" lettering on their boilers.
 * Red wheels.
 * External brake shoes.
 * Black domes and crossheads.
 * Brake pipes.
 * Yellow wheel lubricators on both sides, that connected to their valve gears.
 * Yellow siderod guards.
 * Black rivets on their front bufferbeam and coupling hook bases.
 * Series 19:
 * Their crossheads became grey again.
 * The text on their nameplates became gold.
 * Series 21:
 * Their crossheads became black again.

Texture variants
In addition to their standard livery, a few other texture variants exist of Bill and Ben's CGI models. These texture variants include:

Fonts
The following fonts were used on Bill and Ben's Gauge 1 models:
 * Times New Roman
 * Franklin Gothic Bold
 * Myriad Pro Bold

Voice Actors
Bill:
 * Jonathan Broadbent
 * Tim Whitnall
 * Rasmus Hardiker
 * Tomoko Naka
 * Noriko Shitaya
 * Sakura Yoshioka
 * Sascha Draeger
 * Marek Bocianiak
 * Christian Greger Strøm
 * Scott Maurstad
 * Reinder van der Naalt
 * Alan Bravo
 * Dor Srugo
 * Yehonatan Magon
 * Silas Borges
 * Salvador Serrano Jr.
 * Miguel Ángel Poison
 * Antti L. J. Pääkkönen
 * Sasu Moilanen )
 * Anton Savenkov
 * Loukas Frangoulis

Ben:
 * Jonathan Broadbent
 * Matt Wilkinson
 * Miyuki Hara
 * Hiromi Nishida
 * Noriko Shitaya
 * Sakura Yoshioka
 * Sascha Draeger
 * Wojciech Chorąży
 * Anders Sundstedt
 * Scott Maurstad
 * Reinder van der Naalt
 * Carlos Domínguez
 * Miguel Ángel Leal
 * Yehonatan Magon
 * Silas Borges
 * Miguel Ángel Poison
 * Alfredo Martínez
 * Salvador Serrano Jr.
 * Joonathan Kettunen
 * Anton Savenkov
 * Loukas Frangoulis