Continuity mistake: When Timothy says "See you met Marion then," the last truck changes between shots.
Continuity mistake: In the flashback, Gator has three trucks at first, but when he conquers his fear and crosses the bridge, he has a fourth one.
Continuity mistake: When Thomas puffs away from Marion, his trucks change from red to green.
Continuity mistake: When Thomas first arrives at the Clay Pits, Timothy can be seen with a train of trucks. In the next scene, they have disappeared.