"Gay Dude" will be directed by Chris Nelson and features a script by Alan Yang. The cast also includes Sarah Hyland (Grey Gardens), Nicholas Braun, Hunter Cope, Gary Cole, Brian Geraghty, Dakota Johnson and Dreama Walker.
In the film, Braun and Cope play two best friends, Matty and Michael, respectively, who are determined to lose their virginity before their senior prom. However, their journey takes an unexpected turn when Matty tells Michael he's gay.
Mullally will play the mother of Cope's character, and Offerman will play the father of Braun's character.
Mullally has been seen on Broadway in Young Frankenstein, Grease and How to Succeed in Business Without Really Trying. She is best known for her Emmy Award-winning role as Karen Walker on NBC's "Will & Grace" and also plays opposite Offerman in NBC's "Parks & Recreation."