Successfully complete World 11 to unlock the 2006 banana meter.
Control main screen
On the "Start Game" screen where AiAi is dancing, there are flowers under him. Tap them, and they will dance. If you tap birds, they will fly to the top of the screen. Tap a balloon two or three times to make it pop.
Credits mini-game
Successfully complete the game to unlock the Credits mini-game at the options menu.
Secret mini game
On the welcome screen or the screen where AiAi is dancing if you see the ballons floating up then try to pop 10+ to start the score multiplier going. Try beating my record of 167 ballons in a row.
World 11
Successfully complete Worlds 1 through 10. Go to Hollow Diamond, then turn 180 degrees and go slowly up the ramp. Land on the narrow platform below, then turn around again and hit the red gate (Meteorite Mayhem). Go to Converse, then move towards the right edge. Wait for the red platform to pass its vertical angle. Gain some speed and dash at the red gate (Big Bang Boom) to unlock World 11.
World 12
Unlock the 2006 banana meter, then collect 2006 bananas from any World in the main game.
2006 banana meter...