In 3.5, they certainly were normal animals. From the SRD (emphasis mine): "A familiar is a normal animal that gains new powers and becomes a magical beast when summoned to service by a sorcerer or wizard. It retains the appearance, Hit Dice, base attack bonus, base save bonuses, skills, and feats of the normal animal it once was, but it is treated as a magical beast instead of an animal for the purpose of any effect that depends on its type. Only a normal, unmodified animal may become a familiar."
So does everyone agree that a familiar, from day one, can understand every language its master speaks, whether spoken by its master or someone else?