Here is the full list of all 20 Flockers achievements.
Unlock a secret level.
Blow up 999 sheep.
Explode 2 sheep while they are in the air at the same time.
Complete a user-created level.
Complete any level with a customised sheep.
Get 20 sheep into the exit at once within 1 second.
Complete the first 3 levels.
Look at what you’ve hurt.
Three star every level from the first theme.
Three star 2 boss levels
Save 100 sheep from fall damage by landing on something soft.
Collect 20 golden fleeces.
Collect 30 golden fleeces
Get 20 punk sheep moshing together.
Try out 10 different styles of sheep (blood included).
Complete every level (including bonus levels)
Three star everything
Find and unlock all the secret bonus levels
Kill 500 zombie sheep
Have 20 sheep jump at the same time.