Rogatien Lloyd Cumming (31) and Kerry Lee Smith (28) pleaded guilty to one charge each of reckless driving.
The court was told on March 3 about 4.30pm, Cumming went on the roof of the Mitsubishi Magna driven by Smith.
Cumming was holding the roof racks while kneeling, as the car was travelling at 40km/h on Estuary Road.
He lost his balance and fell on his back when the car went over a speed hump, but did not fall off the moving vehicle.
Police prosecutor Sergeant Rod Murray said there were about 25 people, including children, in the vicinity.
‘For their age, this should be past behaviour,’ he said.
‘It was ridiculously stupid.’
Magistrate Vivian Edwards believed the incident ‘beggared belief’ and said it was fortunate Cumming did not fall off the car.
Duty lawyer Brian Mahon said the pair were friends and ‘trying to keep each other happy’.