Curtis Armstrong

Robot DeFault / Marf (voice)

Harland Williams

Monster Krumholtz (voice)

Maurice LaMarche

Gart / Perry / Loudmouth (voice)

Jonathan Slavin

Ogo (voice)

Megan Hilty

J.D. (voice)

Cree Summer

Spitfire / Globitha (voice)

Rhea Perlman

Nessie (voice)

Fred Tatasciore

Punch Morley (voice)

Kurtwood Smith

Mr. Wheelie (voice)

Ping Wu

Master Grabmirist (voice)

Nolan North

Hal Worth-a-ton / Uncle Kuffley / Crikey (voice)

Alan Tudyk

Crazy Cousin Gizmo (voice)

Ruth Williamson

Dame Lady Madame (voice)

Jon Polito

Sir Cranklin (voice)

Jeff Bennett

Snap Winsome / Lil' Lugnuts (voice)

Rob Paulsen

Bob / Scale (voice)

Jeffrey Tambor

St. Crispy (voice)

Bill Fagerbakke

Lev (voice)

April Winchell

Arpa / Grandma 10010 (voice)

Jennifer Cody

Lucy (voice)

Leon Thomas III

Monster's Singing Voice (voice)

Kari Wahlgren

Robo Ono (voice)

Greg Cipes

Vapid Milquetoast (voice)

Harriet Sansom Harris

Bea Holder (voice)

Adam Wylie

Fuzzy Slippers (voice)