Suggestions by @rowenjackson

Jim Carrey

as Grinch in I, Looney

Danny DeVito

as Lorax in I, Looney

Benedict Cumberbatch

as GWDLGEAH in I, Looney

Martin Short

as Sam I Am in I, Looney

Sean Hayes

as Fish in I, Looney

Mike Myers

as Cat in the Hat in I, Looney

Rob Paulsen

as Speedy Gonzales in I, Looney

Russi Taylor

as Granny in I, Looney

Bill Farmer

as Sylvester in I, Looney

Bob Bergen

as Tweety Bird in I, Looney

John Paul Karliak

as Wile E. Coyote in I, Looney

Paul Julian

as Road Runner in I, Looney

Tress MacNeille

as Penelope Pussycat in I, Looney

Bruce Lanoil

as Pepe Le Pew in I, Looney

Kath Soucie

as Lola Bunny in I, Looney

Charles Fleischer

as Roger Rabbit in I, Looney

Kelly Sheridan

as Starlight Glimmer in I, Looney

Joe Alaskey

as Daffy Duck in I, Looney

Billy West

as Bugs Bunny in I, Looney

Robin Williams

as Thedore in I, Looney