Cheswick Jeepers Creepers playing Darry Jenner Dodge Ball: A True Underdog Story playing Justin Redman Voice of Alvin in Alvin and the Chipmunks Accepted playing Bartleby "B" Gaines Live Free or Die Hard playing Matt Farrell Spyro the Dragon in the Skylanders television series. Long attended Fairfield College Preparatory School, a Jesuit school, and Vassar College, where he was a member of the sketch comedy group Laughingstock and starred in several plays, including Butterflies Are Free. He played Warren Cheswick on the NBC TV series Ed, and appeared with John Hodgman in TV commercials for Apple's "Get a Mac" advertising campaign.
He was also a regular on the NBC TV series Ed (2000–04), playing socially awkward Warren Cheswick.
He voiced the character of Alvin in Alvin and the Chipmunks, Alvin and the Chipmunks: The Squeakquel, Alvin and the Chipmunks: Chipwrecked, and Alvin and the Chipmunks: The Road Chip.
He also played the main character in the 2006 comedy film Accepted.
Long made a guest appearance in the 2006 documentary, Wild West Comedy Show.
In 2007, he co-starred with Bruce Willis as a "white-hat hacker" in Live Free or Die Hard and had a role in the film, The Sasquatch Gang.
Long is known for his depiction of a Mac in Apple's "Get a Mac" campaign.
The campaign featured commercials in which Long as a Mac and John Hodgman as a PC engaged in playful banter about "the strengths of the Mac platform and weaknesses of the PC platform." Long also had a small role in the 2008 comedy Zack and Miri Make a Porno, where he plays Brandon St. In 2009, he starred in He's Just Not That into You along with co-star Ginnifer Goodwin and After. He also provided the voice of Humphrey in Alpha and Omega (2010), starring with Hayden Panettiere.
Also in 2010, Long starred in the comedy Going the Distance with Drew Barrymore.
He was cast as a one-armed Civil War veteran in Robert Redford's The Conspirator.