There were two scenes which were in the original script and shot but were cut from the final version of the film. One scene had the Kamp Komfort manager (Brian Doyle-Murray) dress up in a moose costume and sneak into Clark and Ellen's tent to scare them (which explains the "wildlife fun" the manager mentioned as they checked in). That scene was cut because it made the sequence run too long, so it was re-written to have Dinky sneak into the tent instead. The second scene originally written/filmed but cut was one featuring the two Indians (the same ones who see Clark wandering aimlessly through the desert and say "What an asshole") as well as a camel rider who finds Ellen and the rest of the family and rescue them. That scene was cut because, according to Harold Ramis, the camel had been raised in Burbank and had only ever walked on pavement, and the camel did not take to walking on hot sand very well. All the shots of the camel were unusable. Remnants of both cut scenes appear as photos during the ending credits photo montage.
There was a deleted scene that took place after the redneck mechanics clean Clark out of all his money for the car repairs and Clark mentions that they're going to run out of gas. In the deleted scene, they do run out of gas and Clark, Ellen and the kids are forced to push the car(with Edna still inside it) to the nearest gas station. The attendant fills the car up with gas and then Clark drives away very fast without paying for the gas because he has no money. The attendant then runs after them on foot but of course doesn't catch them. That gas station is also where Clark got those sandwiches because later after leaving the Grand Canyon motel, he tells Russ to get out the sandwiches he got at the gas station.
It was originally scripted that after Aunt Edna was tied to the roof of the car and there was a shot of her fingers moving implying she was, in fact, still alive. This was considered "cruel" to have a live person on the roof of a car by the ratings board, so it was cut and she remained dead.
The Other Darrin: While Chevy Chase and Beverly D'Angelo kept reprising their roles as the Griswold parents for the first four films, their kids were played by different actors each time: Anthony Michael Hall, Jason Lively, Johnny Galecki and Ethan Embry played Rusty while Dana Barron, Dana Hill, Juliette Lewis and Marisol Nichols played Audrey. Dana Barron is the only one to return to the role—she plays Audrey in the Cousin Eddie Christmas sequel—although she, Juliette, Anthony and Jason all appeared in an Old Navy commercial spoofing National Lampoon's Christmas Vacation.
Today, finding out if the park is closed would be as simple as checking its web page, and because of the prevalence of GPS, getting lost driving across the country would be much more difficult.
Also, Clark's payment problems after he's strongarmed out of his cash would not be that much of a problem nowadays considering that debit payments from his bank account is common and credit cards are accepted in far more places now.
Throw It In!: Many bits in the film were improvised including Clark's dance with his sandwich, Clark's send-off to Aunt Edna, Rusty putting his feet up on the driver's seat and Rusty chugging of the beer.
The Griswold's destination was originally supposed to be Disneyland, as it was in the short story, but it was rejected since the park is open year-round and thus the ending with John Candy wouldn't have worked.
The ending was originally completely different. Clark would hold up Roy Walley in his home and force him to sing and dance, and the police arrive to arrest Clark, when it's revealed that the mysterious woman in the red car is actually Roy's daughter. She convinces her father to drop the charges and the family goes on a flight back home after receiving Walley World hats, but they discover that they caught the wrong flight and Clark forces the pilot to turn the plane around. Negative test screenings made the filmmakers rewrite the scene.
Matty Simmons and Warner Bros executive Mark Canton wanted John Landis to direct this movie. Simmons talked to him about it, but Landis turned it down because he was working on An American Werewolf in London at the same time.
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.