[4] O'Malley became good friends with actors Josh Gad and Leslie Odom Jr. at Carnegie Mellon University.

[8] He starred as Richie Cunningham in the 2006 Los Angeles premiere of Happy Days, as well as the 2007 Goodspeed Opera House production.

[9][10][11] In October 2008, he appeared alongside Colin Donnell and Laura Osnes in the then Broadway-bound musical Pride and Prejudice as Charles Bingley, at the Eastman Theatre in Rochester, New York.

[12] O'Malley's first appearance on Broadway was in the musical The 25th Annual Putnam County Spelling Bee, replacing actors in the roles of Leaf Coneybear, William Barfee, and Douglas Panch.

[22] O'Malley also participated in the Dustin Lance Black play 8, a chronicle reenactment of the federal case that overturned California's Proposition 8.

He created it after joining the Hamilton cast; he realized that young fans of the show were seeing an unrealistic and cultivated depiction of the life of a Broadway actor.

This year we were honored to receive the 2010 Human Rights Campaign Community Award and even participated in the ING New York City Marathon as a charity team.

[35] On July 21, 2013, O'Malley announced his engagement to boyfriend Gerold Schroeder via Facebook,[36][non-primary source needed] and they married on September 28, 2014.

[39] Via posts on Instagram, Facebook, and Twitter, O'Malley announced on November 22, 2018, "after more than two years of paperwork, home studies, joy, heartache, and grace" he and Schroeder had adopted a newborn baby boy.