Duke is a large black & gray train with a very modest personality.
In Season 1, he was portrayed as evil, violent and destructive. (This was due to the fact that he was infected with a virus). In his healthy state, Duke looked kind, quiet, and willing to do anything to help his friends.
In Season 2, he is portrayed as one of Train X's henchmen, mostly stealing orbs for Train X and causing mischeif.
- His eyes turned red when he was infected, after being cured from the virus, his eyes were gray, and in season 2, they were black.
- When he laughs and speaks, the movements are very subtle
- When Duke speaks in Season 1, it is visible that Duke doesn’t have a mouth for some reason, but in season 2, Duke has a mouth when he speaks
- Duke becoming an antagonist in season 2 was widely criticized for reverting most of his character arc.
- In Victor Arrives, It is noted that Duke almost killed Kay when he was infected, but luckily Victor arrived on time.
- In Another World, Duck the leader of a wholly different Train World revealed that because of Kay (in which he is a betrayer in this world) he destroyed Duke's engine and trapped him somewhere in the Time Tunnel but was later revealed that he told that Kay (who is from his world) was locked up in the Time Tunnel.