Surfing jokes begun when Mega Man reprogrammed Rush to be able to transform into a jet. While using Rush to get across a chasm of Disappearing Blocks, Mega Man adopted a surfing pose but was disappointed when Rush told him that surfing jokes wouldn't be permitted while flying on him.
Since then, the "surfing" on another character has been used by "surfboards", "surfers" and spectators alike.
Another exampe is when Rush was riding Bass (who was combined with his support unit, Treble) to Dr. Wily's fortress. Bass told Rush not to tell surfing jokes.