Before animation, Klassen worked in radio in Winnipeg (CITI-FM), Toronto (Q107), Calgary (CFAC), Portage la Prairie (CFRY) and part-time at CFOX and CFMI.

Klassen has also voiced many characters including Sylvester in Baby Looney Tunes, Tusky Husky in Krypto the Superdog, and Tony and Seth Parsons in The Cramp Twins.

He is the voice director for shows and films including Martha Speaks, Johnny Test, Max Steel, George of the Jungle, Ed, Edd n Eddy, the Barbie franchise, Transformers, Cardcaptors, Salty's Lighthouse, G.I.

Joe, Pucca, My Little Pony: Friendship is Magic, Littlest Pet Shop, and Pac-Man and the Ghostly Adventures.

Klassen is also a writer and owned a production company with Ian James Corlett which helped with localizations,[1] and also he was a story editor on the Bakugan series.