Flowerbelle is Flowerbelle Lee (after the character played by Mae West in the move My Little Chickadee). Now - Flowerbelle is very petite, unlike her namesake - but she needed to be a tough, strong girl to survive - and she lived up to her name on that one.
Shelly is Sheldon Kornpet (DDS) - after the character in the In-Laws. I haven't seen the remake (and won't). He is named after the character ALAN ARKIN played. "What a guy!"
Lazlo is Lazlo's last name - he is named after the CRAZY lawyer in the movie Where the Buffalo Roam. His full name is Carl Lazlo (Esq.) - and he is crazy, and would make a great anti-social commune-loving terrorist.
Spooky is Spooky Underfoot. I think that's self -explanatory.
Tuxedo - I guess that's his last name too.
He is named after Tennessee Tuxedo - the cartoon character. And he IS a character!
...and Ming Loy don't have an official last name. But she has two first names.