Certain familiars give you stat bonuses. Here is a list of these:

Chicken - +1 Strength, +1 Agility, +1 Defense
Snoot - +2 Strength
Spiny - +2 Defense
Snailburt - +5 Defense, -5 Agility
Scratchpaw - +1 Strength, +2 Agility
MeowBurt - +3 Agility
Beholder - +2 Magic