Round the Twist (7 Network children's comedy series, 1989-2001)

Episode 1.08: Wunderpants: In which Pete puts his underpants in the microwave to dry them and discovers that wearing them gives him super powers - which is how he's able to drag his school bus out of trouble with his bare hands. The bus in question is former Melbourne 531, a 1953 AEC Regal III with Martin and King body: