The actress, 29, will make her debut in the 6th episode of the season as Reagan, a pharmaceutical sales rep who comes to town on business and rents out Jess' (series star Zooey Deschanel) room while she is sequestered on jury duty.
Fox, who most recently appeared in "Teenage Mutant Ninja Turtles", was the obvious choice for her comedic skills, reported theWrap.
"It's insane to me that such a gorgeous person can be so funny, but I guess we just all have to accept it. I've been a fan of her comedic skills since 'This is 40,' and I'm so excited to have her on the show. We had Megan in mind when we wrote this part - she's the perfect person to come in and shake these guys up," said executive producer Liz Meriwether in a statement.