In the scene where the Griswolds are in the parking lot staring at Walley World, they are actually looking at the Santa Anita Racetrack. Harold Ramis said they cut the racetrack out of the frame, and replaced it with a hand painted picture of Walley World.
When they filmed the footrace in the parking lot, it was 105 degrees Fahrenheit outside, and the pavement was 130 degrees Fahrenheit.
Originally, the producers wanted Christie Brinkley to appear naked in the film, but she refused. A compromise was reached, where she stripped down to her bra and panties before jumping in the pool with Clark.
Chevy Chase said that many of the rides at Walley World made him and the other cast members vomit, especially since they all had to ride them several times for each take.
Clark’s dance with his sandwich was improvised.
Rusty’s chugging of the beer was also improvised. Nice….
According to Rena Fruchter’s 2007 biography “I’m Chevy Chase…and You’re Not”, Harold Ramis and Chevy Chase did uncredited re-writes of the screenplay, shifting the focus from the teenagers to the parents. For instance, the Ferrari Girl (Christie Brinkley) was originally to be a thirteen-year-old love interest for Rusty instead of Clark.
Chevy Chase and James Keach stated in interviews that during the “Dog tied to the bumper” scene, both of them were legitimately tearing up, and that Chevy consistently biting his lips and his shortness of breath were genuine. All because they were trying so hard to contain themselves from laughing.
The theme park that served as Walley World was actually Six Flags Magic Mountain in Valencia, California.
Imogene Coca originally turned down the part of Aunt Edna, because she did not think she could portray such a mean character. Even during filming, she was often concerned that she was being too mean to her fellow cast members.
The movie was based on the article “Vacation 58” by John Hughes, which appeared in the September 1979 issue of National Lampoon Magazine.
Daisy Mabel (Cousin Eddie’s tongueless daughter) was played by director Harold Ramis’ daughter Violet.
The “W” in Clark W. Griswold stands for Wilhelm.
The poster art was by fantasy illustrator Boris Vallejo, and is a parody of the poster art for Conan the Barbarian (1982).
The Star Ford car dealership in Glendale, California, the location scene where Clark purchases the Wagon Queen Family Truckster, is located two blocks north of Chevy Chase Drive.
Originally the movie ended with the Griswolds holding Roy Walley and his family hostage in their house. However, test audiences hated this. So, they reshot the ending as we know it today.
They did partially re-create this ending though in National Lampoon’s Christmas Vacation (1989).
In the Walley World scenes at the end, Anthony Michael Hall is actually taller than Beverly D’Angelo. In previous scenes, they were the same height but Hall grew three inches between the original filming and the reshoot four months later.
John Candy was paid $1 million for his brief appearance at the end of the movie.