Here is the full list of all 9 Hooklings achievements.
Make a four hit combo.
Make a six hit combo.
Reach the first checkpoint at 20 levels.
Win against the boss.
Survive the skull for 60 seconds.
Transform every enemy into a cherry for three levels in a row and eat them all.
Don't move (and don't die) for 20 seconds.
Don't pick up any fruit for seven levels in a row.
Finish the game from start to finish without using any continues.