In the episode "The One In Barbados (2)" when Mike and Monica begin playing table tennis, Mike states the rule that if you place your hand on the playing surface you forfeit the point.

In the next scene when they are playing and Mike is on 'game point', while stretching to hit the ball he cleary places his left hand on the table during the rally and then goes on to win. By applying the rules he stated earlier, he should have forfeited that point.