In order: DAFFY (re: crazy) Duck, Stoop Kid (an agoraphobic who fears leaving his stoop), SCREWBALL (re: insane) Squirrel, 2 STUPID dogs, PINKIE (re: her color) Pie,
Freddy the Devil (nicknamed as "The Red Guy" throughout the show and "I.B. Red Guy", Popeye (named for his "popping out" eye, a possible byproduct of Grave's Disease), FAT Albert, I.R. Baboon, named for his inability to spell, Ed Bighead (named for his giant head and ego), Hans Moleman (named because he looks like a mole-man hybrid), and lastly Dr. Lipschitz, named presumably for his quack advice.
