In a two player game, get both Ice Climbers up to the lowest level of the bonus round (so you are standing on the blue unbreakable bricks, but haven't actually activated the bonus round yet). Wait for a bird to come and kill one Ice Climber, but just as the resulting white ghostly figure reaches the peak of its "jump," have the other Ice Climber land on the higher platform, activating the bonus round. The Ice Climber that should have died now can jump nearly twice as high as it should be able to. This ends at the end of the bonus round, though.