Rex is a Green Arlesdale Railway Tender Engine. He, along with Jock, was away from The Arlesdale Railway for quite a long time Being overhaul and then return home with Jock to get The Arlesdale Railway running again.
Appearences:[]
- Season 1: Toby and the New Engine (mentioned)
- Season 8: Tick-Tock-Jock (mentioned)
- Season 9: The Arlesdale Rumor (mentioned)
- Season 15: Tyrannical Rex, Jock Beats the Clock, Ice Ice Daisy (cameo) A Christmas Caroline. (cameo)
He is likely to appear in Season 18.