This is awesome! My nicknames are:
Steph, Crash, and Stephi (pronounced Shtephi-it is in German class!)

Jesse is:
Jes, Beasty, and Sweety

Sammy is:
Sam, Princess, and Furball Fluff!

Splinter doesn't have one, but my parents kitties do!

Peek-a-Boo is:
Boo

Autumn is:
Matumn and Tumn Tumn

Steph, Jesse, and Splinter