5. Unlock the additional levels in each stage

Each stage in Cut the Rope 2 has 20 levels but you can unlock an additional 5 by doing one of two things: either find all the medals in that level pack or finding the missing shamrocks. If you don't want to do that, you can buy the additional levels in each pack for $0.99 each. But who wants to do that? I've found the shamrocks aren't too terribly hard to collect but medal missions create more of a fun challenge in themselves. Watch for them after you complete a level. Just tap on the medal to see what you have to do in order to earn it and replay those levels.