A character from my current story/worldbuilding project. He's from the maintenance crew who keep the great Trains safe and rolling. Working animal companions are a rarity, but some maintenance crew keep rats as companions to fetch things when the worker is in a small, enclosed space, or to help find pipes leaking poisonous gasses or fluids. Such rats get their own uniforms so that people will know to leave them alone and not mess with them.

This is a domesticated giant pouched rat having a nap on his maintenance crew pal's arm.