In order to save money, the filmmakers decided to not get trailers for the actors, and instead decided to rent a house for the duration of filming (approx. 6 weeks), where the actors could go between takes. The house turned into a popular hangout spot for the cast and crew, and they would often go to the house even during weekends or days off.
Sam Rockwell would often improvise and joke around on the loudspeaker during scenes. One time, forgetting that there were children around, he made an inappropriate joke about herpes, which upset the owner of the park. Rockwell had to go and apologize so that they could continue filming.
The script was written in 2007 as "The Way Back", but the title was later changed to avoid confusion with the film The Way Back (2010). The title refers to the "way back seat," the 1970s colloquial expression for the third, often-hidden seat located in the cargo section of a station wagon.
While location scouting, Jim Rash would take pictures of beach houses that he felt would be good to film in. During filming, he discovered that one of the houses he photographed belonged to Steve Carell's in laws.
Steve Carell initially turned the movie down because he and his family go on vacation to his home state (Massachusetts) every Summer. However it was later discovered that the location of the film shoot was a short drive away from where Carell and his family vacationed, therefore he was able to accept the role.
The name of the water park Duncan works at in the movie is called 'Water Wizz'. In the first Grown Ups, the water park the families go to is also called 'Water Wizz'. Both films star Maya Rudolph. It was shot in the same park.
In the original script, the character of Caitlin was a young teenager who worked in the park and had no significant screen time. In later drafts, Jim Rash and Nat Faxon decided to make the character older and have her interact with Owen (Sam Rockwell)more, though it was mostly superficial interaction. When Maya Rudolph was cast, Rash and Faxon told Rudolph and Rockwell, that although there was not much in the script, the two actors would have to create a meaningful relationship between their two characters.
When Owen is giving Duncan a ride home he says, "I hate clowns. Kidding. Except for the part where I really do hate them." Sam Rockwell, who plays Owen, starred in Clownhouse (1989). He plays one of three young brothers that are terrorized by three escaped mental patients who are dressed as clowns.
A documentary called Wagonmasters (2012), released the year before this movie, discusses the importance of the "wayback seat." Promotional items released for _Wagonmasters_ included bumper stickers and buttons declaring proudly, "I sat in the wayback."