Alexander is famous in Hollywood for playing the role of Shane in the small screen project, Weeds. In the year 2000, he started his acting career with a small screen project, Freaks and Geeks and also did another TV series, The Geena Davis Show, in the same year.
In 2001, he portrayed the role of Josh in the small screen project, Family Law and did Boomtown which is a small screen project, released in 2002. He lent his voice to the character of Nemo in the silver screen project, Finding Nemo, which was released in 2003. In 2006, he portrayed the role of Twist in the movie, How to Eat Fried Worms.