Following graduation, she began performing improvisation at iO Theater, where she appeared on the Harold team Blue Velveeta.
[1] Messing is an ensemble member of Annoyance Theater where she performed in "Co-ed Prison Sluts," "The Miss Vagina Pageant," "The Real Live Brady Bunch" as well as directing What Every Girl Should Know... An Ode to Judy Blume (based on the work of Judy Blume).
[2] Susan is a founding member of The Annoyance Theater (1989) where she has created roles in over thirty original productions including Co-Ed Prison Sluts (the longest-running musical in Chicago), That Darn Anti-Christ, The Real Live Brady Bunch and the famed Judy Blume adaptation, What Every Girl Should Know.
In a favorable review, Ryan Hubbard of the Chicago Reader wrote that her skill improvising with others, "…is a testament to her congeniality, experience, and broad intelligence.
Susan married former Saturday Night Live and Sesame Street writer Michael Clayton McCarthy on September 30, 2012.