A Gymnomi Slime Advanced Steam locomotive. This is similar to an Earth design called a Golwé. The entire locomotive is a rigid frame with two independently swivelling wheelsets, as on a double Fairlie. This loco has a unique return-flue boiler, where both the smokebox and firebox are at the same end of the boiler. This keeps the smoke away from the crew cabs at either end.
Advanced Steam locomotives were introduced during the pan-Gymnome Oil Crisis of the 2330s as an alternative to diesel locomotives. They include modern technology such as electronic control stands, automated firing, climate controlled cabs, gas producer combustion systems to fully burn their solid fuel, feedwater heaters, superheaters, water recondensators, compound expansion of steam--the works!
The conductor-brakegoo, Limerenayde, is a centauroid Gymnomi. They're a little bit of a tight fit in the cab of the locomotive, but they're made out of goo after all so that's not too big of an issue.