Here is the full list of all 13 Chicku achievements.
Break your legs while landing.
Unlock three hats.
Die one hundred times in a single level.
Stay airborne for one minute.
Kill ten mosquitoes in one level.
Play a brawl game with ten or more modifiers.
Die one second after hatching.
Complete the first world in Chicku.
Complete the second world in Chicku.
Complete the third world in Chicku.
Unlock fifteen hats.
Complete a hell map without dying once.
Complete all hell maps.