The actors agreed to do the third film as long as there wasn't a fourth movie. Bradley Cooper, Ed Helms, and Zach Galifianakis felt the story had lost its momentum. Cooper took convincing to do the project from Galifianakis.
Grant Holmquist, who performed the role of baby Tyler/Carlos in Hangover (2009), returns to portray toddler Tyler/Carlos in this film.
Bradley Cooper, Ed Helms, and Zach Galifianakis were each paid $15 million (plus a back-end deal), 25 times their respective salaries for Hangover (2009).
In 2012, Zach Galifianakis lost so much weight that he had to wear a prosthetic belly for this film.
Chow appears in all three films, even though he was originally only cast for the first film. Zach encouraged the filmmakers to have Chow written into the sequels.
Todd Phillips: Playing as Mr. Creepy again in the motel room in a bathrobe paying off a prostitute as Mr. Chow is parachuting across his Las Vegas hotel room window.