Complete each achievement to get the gamer score.
Unlockable How to Unlock
Absurd Amphibian (10) Become a Frog-Clyde
Ancestorial Antics (14) Become an Ape-Clyde
Battle Addict (12) Play Versus mode
Becoming Baaaad (8) Become a Sheep-Clyde
D.N.Ain't (16) Become a Mutant-Clyde
Dupliclone Dash (18) Complete levels 1 - 24 and 10 Challenge levels under par time
Foolish Freedom (20) Exit 75 clones through the ventilation shafts
Kenn Collection (15) Collect 50 of the cloned Killer Kenn Action Figures
Killer Kudos (25) Collect 100 of the cloned Killer Kenn Action Figures
King Clyde (20) Complete all of the Super-Challenge Levels
Master of all Clyde-Dumb (30) Complete the Game
Poultry Party (12) Become a Chicken-Clyde

Unlock Mutant Clyde
To unlock Mutant Clyde, simply beat all levels under par time.
Unlockable How to Unlock
Mutant Clyde Beat all levels under par time