He first appeared in Race Around Umi City when he popped Sam's balloon. He even made fun of UmiCar because he was so small. He also cheated by raising the drawbridge, dumping dirt on Team Umizoomi, and dropping soap that made UmiCar slide so much he broke his steering wheel. He and UmiCar raced to the finish line, but UmiCar won. Sam shared his balloons with UmiCar and Team Umizoomi, and UmiCar gave Dump Truck a balloon. He was sorry for being mean with popping Sam's balloon, laughing at UmiCar, and for cheating. His face looks somewhat mean.
However, in The Great Shape Race, he was still selfish and a cheater. He wanted the magical dodecahedron for himself. This time, he didn't laugh at UmiCar, but he self-proclaimed himself to his rival. He cheated by not waiting for go, cutting the rope to get over the cliff, dropping glue everywhere, and destroying the car path. UmiCar still won in the end and shared his flying powers, granted by the dodecahedron, with Dump Truck. This time, he was really, really sorry for cheating and being selfish.
He also appears in UmiCar's Birthday Present as one of the guests. He was not like he was in the other episodes. He was happy and kind. It must be because he promised to be good on UmiCar's big day.
In Umi Grand Prix!, Dump Truck returns to win the aforementioned race. When Team Umizoomi, UmiCar, and Shark Car come up to Dump Truck, he first tries to stop them with wet cement. When the Team catches up, he tries pooting enough smog to obscure sight. After UmiCar and Shark Car passed him, he threw major tantrum only to throw wet cement all around him. Later he congratulated them for winning the race by defeating the Troublemakers.
- Dump Truck might be based off of Nintendo's Wario from Super Mario Bros series.
- Dump Truck is the only character to be an antagonist both times he appears, but the second time, he's more proclaimed as UmiCar's biggest rival.