Grab a Melon Bug (the bug that curls when you approach) and take him to the Shy-Guy Pipe (where the Shy Guys appear from). Look up and shoot the bug. If done correctly, the bug should fall in the tiny space on the right side of the pipe, between it and landscape. Stand on the elevated surface and make sure you have no eggs. The Shy Guys will pop out towards you, but hit the bug. You will keep getting extra lives until you have 100. Then, get a perfect completion on World 5 and you will get the roulette game. If you get the X3; you will get 300 lives.