Perform the followings steps to unlock every world without playing through the game:
1. Load up Angry Birds and go to the world select screen.
2. Center a locked world on the screen.
3. Push back button all the way out of Angry Birds.
4. Load Angry Birds back up and, when the "Play" button appears, rapidly tap it.
5. You should be inside the locked worlds stage select screen.
6. Now, pass the first level of each world to unlock it.