In 2002, Carlson appeared on the Broadway stage for the first time in Edward Albee's The Goat or Who is Sylvia?. The next year, he starred in the Broadway revival of Molière's Tartuffe. Shortly after, he played the role of Marilyn in Boy George's Broadway musical Taboo, for which he received a Drama Desk nomination. He then began his television and film career with a role in the romantic comedy Hitch starring Will Smith.
In 2006, he first appeared on the very television show for which he received his name: All My Children. His groundbreaking onscreen character was a British rockstar named Zarf, who discovered though an arc on the series that she was a transgender woman, transitioning as Zoe. She also falls in love with a lesbian character, Bianca. Zoe's journey throughout the television series showed her attending support group sessions and meeting with an endocrinologist for gender-affirming healthcare.