Sparky is an Aquarius. The description fits him perfectly.

"Aquarian pets are somewhat unusual, eccentric or even a little rebellious. Aquarians are extremely curious and sociable, but can also be erratic and unpredictable. You never know just what your Aquarian pet will do next. Aquarians don’t take well to training or discipline."

Fritz is a Pisces. I can't believe how accurate these are!

"Pisces pets understand your feelings and needs. And Pisces loves to comfort you when you're feeling down. Pisces pets are very sensitive and like plenty of affection which they are always happy to return. Good apartment pets, they tend to stay indoors and don't mind solitude. "

Hans is a Libra. This description isn't quite as accurate as the other 2.

"Libra loves almost everybody and hates being left behind. Libras consider themselves to be members of the family. Very concerned with grooming and appearance, they never mind being pampered or fussed over. Libra is definitely a lover, not a fighter."