Guitar nerd alert: The bass that Rudd plays when he and Segal first jam in Segel's character's garage is a Geddy Lee (bassist for Rush) Signature Fender Jazz Bass, one of the company's best-selling models.
J.K. Simmons, who plays Rudd's father, is only 14 years older than his "son."
Rush actually played an hour-long set for fans who assembled to help shoot the scene where they play a "secret set" at a club.
Matt Walsh's cameo as an impatient golfer comes from his character in a skit performed by the comedy group The Upright Citizens Brigade. He wears the exact outfit from the original 1990 skit for the scene.
Rudd and Segel reprised their roles for a video shown on Rush's 2010-2011 Time Machine tour: The pair crash Rush's backstage area in character and Segel eats drummer Neil Peart's sandwich.