Dr. Seuss/Regular Show

The Cat In The Hat as Mordeca

Sarah Hall-Small as Margaret

Sam-I-Am as Rigby

Norval the Fish as Benson

Horton the Elephant as Skips

Mack the Turtle as Pops

Joey as Muscle Man

Mr. Brown as High Five Ghost

The Grinch as The Evil British Taxi (Ello Gov'nor)

Wickershams as Evil Hot Dogs

Morton the Elephant Bird as Don

The Lorax as Doug

Matthew Katroon as Jimmy (boy)

Pam-I-Am as Eillien

Yertle the Turtle as G.B.F

Little Cat Fleep as Mordecai's Friends

North-Going Zax as Iacedrom

South-Going Zax as Ygbir (Igir)

Aunt Myrtle as Susan

King Derwin as Mr. Maellard

Jane Kangaroo as Starla

Little Cat A as Low Five Ghost

Little Cat B as a small boy

Cindy-Lou Who as Margraet's Friends (one makes a cameo in Regular Show)