Have Eets reach the end of level cake with at least two items remaining in your inventory. Do not try collect any treats, and simply move to the exit. This is possible on the following levels.

Achievement	How to unlock
Level 1-12	Place a bomb next to the top whale and launch it to free Eets.
Level 2-03	Select the middle flower to launch the snack onto the right platform, then launch Eets there.
Level 2-10	Place a beehive to the right of the middle onion. Shoot it off the platform, then rapid-fire at Eets to also push him off.
Level 2-11	Shoot a bee at Eets as he is about to turn on the leftmost platform. He will make an angry jump directly into the cake.
Level 3-06	Place a pepper in front of Eets and explode the cart directly below and slightly to the right of the offending crystal.
Level 3-09	Place a vertical plank in Eets' jump path and he will drop directly onto the cake.
Level 4-12	Activate the fan immediately to hand Eets a snack, which will let him jump into the cake properly.