The Grim Adventures of Billy & Mandy

When Billy and Irwin exclude Mandy and Grim from helping them build a go-kart to enter the Annual Endsville Go-Kart Competition, the latter two decide to build their own. Billy-Irwin, and Mandy-Grim compete against Mindy, Sperg, and a mystery racer (Pud'n). Mindy gets stuck in highway traffic, Billy-Irwin's car is destroyed, Sperg and Grim mutually prevent each other from winning, and Pud'n wins in his little red wagon.