His first role was an unpaid appearance in a Tim Hortons summer camp commercial. That appearance eventually landed him a position in a Pillsbury commercial in which he poked the Pillsbury Doughboy, his first role with lines. He found not being cast in commercials after auditioning "really disheartening" but, in 1999, Cera was cast as Larrabe Hicks in the Canadian children's show I Was a Sixth Grade Alien, which ran for two seasons. That year, he also appeared in the television films What Katy Did and Switching Goals starring the Olsen twins. Cera then made his theatrical film debut in the science fiction film Frequency (2000) as the son of Noah Emmerich's character. Cera also appeared in the films Steal This Movie! and Ultimate G's: Zac's Flying Dream in 2000, the latter of which featured Cera in his first leading role and was presented in IMAX theaters. Cera appeared in several television films in 2001 including My Louisiana Sky and The Familiar Stranger and also began voicing Josh Spitz in the animated series Braceface, continuing to do so until 2004. In 2002, Cera played the young Chuck Barris (played by Sam Rockwell) in the George Clooney-directed film Confessions of a Dangerous Mind. He provided the voice for Brother Bear – an anthropomorphic bear – in the 2003 The Berenstain Bears animated series, which aired for three seasons.