Was originally envisioned as a sequel to Mr. & Mrs. Smith (2005) after that films TV series continuation/pilot failed to be picked up; however the idea was scrapped when Brad Pitt & Angelina Jolie turned down the offer with both stars feeling the original idea was not good enough.
At one point in the movie, Zach's character is asked to put on his pants twice. A direct nod to The Hangover in which Phil claims it is weird to have to ask him twice to put on pants.
According to Isla Fisher, Jim Carrey was originally cast as Jeff Gaffney, but ended up dropping out.
According to website Cinema Blend, actors Jon Hamm and Zach Galifianakis actually "are old friends".
Actress Isla Fisher appreciated Jon Hamm's action hero chops, which extend beyond high-speed chases. Fisher said: "He can smash something with his elbow while kicking in a door and pulling out a gun".