Birth: 04-04-1964 , Atlanta, Georgia, U.S.A.
Cross was born in Atlanta, Georgia, the son of Susi. Cross' father is from Leeds, England. Six months after his birth, Cross's family moved to Florida. After additional moves to New York and Connecticut, the family settled back in Roswell, Georgia, where Cross remained for nearly a decade. His father was often absent, and his family was poor. Cross and his family were evicted from their home while living in Georgia. He spent some time living in motels and at friends' homes while growing up.[3] Cross has been estranged from his father since age 19, although they both currently reside in New York City. He has two sisters, and once bailed his youngest sibling out of jail. He attended Northside High School of the Performing Arts (now North Atlanta High School), graduating in 1982. Cross was elected treasurer of his senior class and was voted "Most Humorous" by his classmates.

Cross began performing stand-up comedy at 17. The day after he graduated from high school, Cross went to New York. Lacking a plan, he drifted around, working briefly for a lawn care company in Long Island, and later enrolled at Emerson College in Boston. He would drop out after only a semester, but during his time there he discovered his new favourite things: partying and sketch comedy. Cross joined This is Pathetic, a college sketch group, where he met John Ennis. In the summer of 1985, the two aspiring actors took a road trip to Los Angeles, although this did not significantly further their acting careers. In Boston, Cross began to perform stand-up more regularly. From the mid-1980s to the early 1990s, Boston had a booming comedy scene, although Cross did not fit the types of acts being booked most of the time. He recalls that it was "a loud-, dumb-, pandering-, racist-, homophobic-type scene". In 1990, a new comedy scene began to emerge at the famous comedy club chain called Catch a Rising Star (where many of the comedians of the 1970s and 1980s got their start). Cross—along with Janeane Garofalo, Louis C.K., and other comics—appeared regularly several nights a week. Cross formed the sketch comedy group "Cross Comedy" with twelve other performers, and they put on a new show every week. They were known for playing tricks on the audience, such as introducing fake comics or planting fake hecklers. Cross became increasingly focused on his comedy work. Cross performed at the alternative comedy club Un-Cabaret in Los Angeles.

Cross began his professional television career as a writer on The Ben Stiller Show. The short-lived Fox Network series hired him toward the end of its run, and he occasionally made brief appearances in the sketches. He had a speaking role in "The Legend of T.J. O'Pootertoot", a sketch written almost entirely by Cross. It was during this period that he first met Bob Odenkirk, with whom he would later co-create the HBO sketch comedy series Mr. Show in 1995. Cross won an Emmy for his work on The Ben Stiller Show in 1993.

In 2004, Cross provided voices for a Marine in the Xbox game Halo 2, and a store clerk named Zero in Grand Theft Auto: San Andreas. He also was the voice of the violent, alcoholic "Happy-Time Harry" doll and Bert Banana in Aqua Teen Hunger Force (although the part was credited as Sir Willups Brightslymoore). He has also made guest appearances in the Adult Swim series Tim and Eric Awesome Show, Great Job!. He directed the music video for The Black Keys' song "10am Automatic", a spoof of public-access television. Cross at the 2007 Plug Awards, Irving Plaza, NYC, February 2007.

In 2005, he contributed to the UNICEF benefit song "Do They Know It's Hallowe'en?". In the Bob Dylan biographical film 'I'm Not There', Cross played the role of poet Allen Ginsberg. Both Bill Lawrence and Zach Braff of 'Scrubs' were ambitious to have Cross cameo on the show as Tobias Fünke, but because of the series' cancellation, the plan never came to fruition.

Cross provided commentary on the Vicarious music video DVD for the band Tool. He has previously performed comedy as an opening act for the band, and its members appeared on Mr. Show several times. He played Ian Hawke in the 2007 movie 'Alvin and the Chipmunks' and Crane in the 2008 movie 'Kung Fu Panda'.

Cross's first UK-only project, The Increasingly Poor Decisions of Todd Margaret, was a comedy pilot for Channel 4 which he co-wrote with writer Shaun Pye, which has been picked up for a full series. Cross's first book, I Drink For A Reason, was published in August 2009.

Cross was raised Jewish, however he is an atheist and does not practice Judaism. As of November 2010, he was dating actress Amber Tamblyn.

In October 2005, he was sued by Nashville club owner Thomas Weber, who accused Cross of taping him without permission for 'Shut Up You F****** Baby' and 'Let America Laugh' in violation of Weber's privacy rights. Weber established a website called wearenotlaughing.com. In April 2006 the case against Cross himself was dismissed and the case proceeded with Warner Music, Subpop Records, WEA Corporation, and the Alternative Distribution Alliance.

Responding to critics of his decision to appear in the critically panned but enormously profitable 'Alvin and the Chipmunks', Cross noted that the film paid for a summer home and more than "all my other projects combined: book, TV show, the two pilots, Year One, yeah." Cross reprised his Chipmunks role in the film's sequel.