Peter Sam, named after the Skarloey Railway's previous controller, Mr. Peter Sam - previously Stuart, after his builder, Kerr Stuart - is a narrow gauge saddletank engine who lives and works on the Skarloey Railway. He is Luke and Jim's cousin.
Peter Sam, named Stuart in his younger days while being brought up under the instruction of Duke, is highly enthusiastic, eager, and bubbly. He can be occasionally cheeky, teasing, and a little cocky, but is kind-hearted, well-meaning, and good mannered. He can also be prone to being a little naïve at times and perhaps take things a little too literally. Peter Sam has a special funnel which makes puffing much easier, after his old one was damaged in a nasty accident with some trucks that broke free from the incline. With an infectious attitude and high spirits, Peter Sam is almost kind and hard-working to a fault, seldom grumbling about late hours or extra work. He is always nice to the coaches and even the trucks, unlike Sir Handel.
Despite being friendly with everyone, when the bigger engines, especially Henry and Duck, tease him or cause him to misunderstand something, he can eventually get aggravated and wish to give them a piece of his mind.
Peter Sam is based on the Talyllyn Railway's Edward Thomas, a Kerr Stuart Tattoo 0-4-2ST. Interestingly, Edward Thomas only donned the Giesl ejector funnel for a limited time, while Peter Sam has used his since its introduction. Four other Tattoo locomotives are also preserved.
In the Railway Series, Peter Sam was painted dark green while working on the Mid Sodor Railway. After arriving on the Skarloey Railway, he was repainted in the Skarloey Railway's red livery with blue-and-yellow lining, with his name painted on the sides of his saddletank.
In the television series, Peter Sam has always been painted dark green with red lining and brass fittings. He has red and gold name and number plates on the sides of his saddletank and coal bunkers respectively.
- Season 100 - Henry the Warrior (cameo), Trouble with Brakevans (cameo), Samson's Waste Dump, Coach Brakes, Scottish Engines, Rheneas' Risky Ride, Ryan and the Snow, Sidney Helps Out (cameo), and Rusty Rescue
- Steven Kynman (UK/US; sixteenth season onwards)
- Shinobu Satouchi (Japan; fourth - seventh seasons)
- Satoshi Katougi (Japan; ninth - eleventh seasons)
- Hiroo Sasaki (Japan; sixteenth season onwards)
- Marios Gavrilis (Germany)
- Sigbjørn Solheim (Norway; sixteenth - seventeenth seasons)
- Gaute Boris Skjegstad (Norway; Blue Mountain Mystery onwards, excluding the seventeenth season)
- Arturo Cataño (Latin America; Blue Mountain Mystery onwards)
- Marek Bocianiak (Poland)
- Paul Disbergen (The Netherlands)
- Antti L. J. Pääkkönen (Finland; Blue Mountain Mystery onwards)
- Tiến Đạt (Vietnam)
- Peter Sam is named after former Skarloey Railway controller Mr. Peter Sam.
- The Reverend W. Awdry's model of Peter Sam is currently on display at the Narrow Gauge Museum in Tywyn. Awdry's model of Stuart was at the Reverend Teddy Boston's Cadeby Light Railway, before the railway finally closed in 2005.
- Peter Sam's large scale model is currently on display at Hara Model Railway Museum in Kyoto, Japan.
- Peter Sam's small scale model (used in Seasons 4-5) with a slate truck was sold at Vectis for £2600.
- Nitrogen Studios went to the Talyllyn Railway and took measurements of Peter Sam's basis; Edward Thomas and other locomotives No.1, No.2, No.4 and No.5 so they could make Peter Sam's CGI model for the Skarloey Railway engines return, in the sixteenth season.
- Peter Sam's small scale model had bent side rods throughout season 4-5.
- Peter Sam has undergone numerous modifications through the television series, including:
- Season 4:
- The special funnel, which appears to be more of a simple square funnel than a Giesl Ejector design.
- Season 5:
- His buffers changed from grey to silver.
- Season 6:
- His buffers were painted black.
- Season 9:
- A permanent tail-lamp was added.
- Peter Sam had Emily's seventh season whistle sound until season twelve.
- Season 12
- His face became smaller.
- Season 16:
- His square funnel was altered to an accurate Giesl Ejector.
- His footplate and sandboxes were painted black.
- He gained a new whistle sound.
- The lower round window on the back of his cab was replaced with two small door, just like his basis.
- A handrail was added across the top of his smokebox.
- His regular one valve whistle was updated to a two valve whistle just like his real counterpart. It also budged up and down until the seventeenth season.
- His cutout windows gained brass frames and contained glass.
- His tail lamp changed to a removable Talyllyn-styled lamp.
- Sanding gear was added.
- His green livery became more vibrant than it was in the ninth season.
- Extra lining near the top of his cab.
- Season 17:
- Permanent lamp and lamp irons.
- His filler cap and dome changed from green to black.
- Season 100:
- His handrails were painted silver.
- His side-rods become silver.
- His trailing wheels became grey.
- His cab handrails became silver.
- Season 4: