Prime

UNKNOWN :
Hivemind
Retractable Limbs
Parasite

MUTATION :
Mismatching Colors (Horns/Claws/Teeth/Hooves/Bones)
Any Shape Pupils
Multiple Eyes
No Mouth
Floating Objects
Extra Mouths
Different Shaped Mouth
Torn Mouth
Missing Limbs
Lack of Paw Pads
Strong Magical Abilities 

RARE :
Werewolf

Rest is Common