Vo filme Vo štvorici po opici hrajú Bradley Cooper (Phil Wenneck), Ed Helms (Stu Price), Zach Galifianakis (Alan Garner), Justin Bartha (Doug Billings), Heather Graham (Jade), Sasha Barrese (Tracy Garner), Jeffrey Tambor (Sid Garner), Ken Jeong (Mr. Chow), Rachael Harris (Melissa), Mike Tyson (Mike Tyson), Mike Epps (Black Doug), Jernard Burks (Leonard), Rob Riggle (Officer Franklin), Cleo King (Officer Garden), Bryan Callen (Eddie Palermo), Matt Walsh (Dr. Valsh), Ian Anthony Dale (Chow's #1), Michael Li (Chow's #2), Sondra Currie (Linda), Gillian Vigman (Stephanie), Nathalie Fay (Lisa), Chuck Pacheco (Hotel Guest at Valet), Jesse Erwin (Hotel Valet), Dan Finnerty (Wedding Singer), Keith Lyle (Casino Dealer), Brody Stevens (Officer Foltz), Todd Phillips (Mr. Creepy), Mike Vallely (Neeco), James Martin Kelly (Police Clerk), Murray Gershenz (Felix), Andrew Astor (Eli), Casey Margolis (Budnick), Ken Flaherty (Old Timer at Gas Station), Joe Alexander (Pit Boss), Constance Broge (Woman in Elevator), Sue Pierce (Mini-Mart Cashier), Floyd Levine (Tailor), Robert A. Ringler (Minister), Britt Barrett (Bridesmaid), Chauntae Davies (Bridesmaid), Alisa Allapach (Bridesmaid), Nicholas Furu (Stun Gun Boy), Angelica Flameno (Stun Gun Girl), Lily Winn (Screaming Girl), Κατερίνα Μουτσάτσου (Eddie's Assistant), Faleolo Alailima (Tyson's Bodyguard), Rio Ahn (Orderly (uncredited)), Joey Brander (Student (uncredited)), John Jason Bailey (Caesar's Palace Pimp (uncredited)), Cody Deal (Roman Soldier at Caesar's Palace (uncredited)), Natalie Cohen (Casino Guest (uncredited)), Carrie Keagan (Casino Guest (uncredited)), Stephanie Mathis (Casino Guest (uncredited)), Guile Branco (Casino Guest (uncredited)), Richard Alan Reid (Casino High Roller (uncredited)), Tom Spano (Casino High Roller (uncredited)), Lanette Fugit Hannah (High Roller (uncredited)), David Hill (Parent Driving Jaguar (uncredited)), Mitch Holleman (Max - Student (uncredited)), Jessica Simons (Casino Guest (uncredited)), Anthony Mingilino (Precision Driver (uncredited)), Michael A. Rizza (Guy in the Elevator (uncredited)), Charlene Geisler (Katie / Girl in the Elevator (uncredited)), Kaitlin Clark (Girl in Elevator (uncredited)), Heather Roop (Mom in Elevator (uncredited)), Joe Satriani (Guitarist in Wedding Band (uncredited)), Carrot Top (Himself (uncredited)), Jaira Valenti (Bartender Hostess (uncredited)), Anat Gerber (Cocktail Waitress (uncredited)), Victor Yerrid (Tiger (uncredited)).