Here is the full list of all 24 Tasty Planet achievements.
Complete the "Park" levels
Complete the "Ocean" levels
Complete the "Picnic Table" levels
Complete the "Outside" levels
Eat 50,000 objects
Eat 1,000 cats (No cats were harmed in the making of this game)
Eat 25,000 objects
Eat 10,000 objects
Eat 5,000 objects
Eat 2,000 objects
Complete the "Laboratory" levels
Complete the "City" levels
Complete the "Sky" levels
Complete the "Orbit" levels
Complete the "Cosmos" levels
Complete all levels
Earn a bronze medal or higher on 30 levels
Earn a silver medal or higher on 30 levels
Earn gold medals on 30 levels
Earn a bronze medal or better on every level in the game
Earn a silver medal or better on every level in the game
Earn gold medals on all levels
Eat 100,000 objects
Beat all three endurance levels