|The code is right here.|
Well, we've got the instructions for you right here!Here's how you do it, as revealed on Angrybirdsnest.com:
1. Open level 13-12 of Ham 'Em High2. Shoot the first Yellow bird anywhere3. Now shoot the White bird backwards and drop an egg on the back side of the hill4. If you hit the right spot the Golden Egg will pop up!5. Once you find the egg you will see the first image below, which opens the Secret Super Bowl Golden Egg level6. If you can pass the level you'll see the second image. Notice that the egg contains the text "Rio"
Or, check out the video below.
Here's the Superbowl ad that revealed the key piece of the puzzle. At 0:27 you can see the numbers 13-12 behind the monkey and below the "Angry Birds" with the question marks. That clue pointed the way to where to start the search.