He appeared in the independent film "Cherry", filmed on the campuses of Kalamazoo College and Western Michigan University, along with several locations in downtown Kalamazoo, Michigan. He plays Aaron, an Ivy-League freshman who falls for an older woman while becoming the object of affection for the woman's young daughter. Gallner played Quentin in the 2010 reboot of "A Nightmare on Elm Street"; his character is the love interest of main character Nancy. Gallner played the brother of Aaron Paul's character in the 2012 film, "Smashed". Gallner played Zach in one episode in the fourth season of AMC's "The Walking Dead". It was initially reported that he would be a recurring character, but his character was killed off, instead. In 2014, Gallner played the role of Kurt, the antagonist to lead character Sam, in the independent film "Dear White People".