Eric Idle and Chevy Chase became friends after filming wrapped up. Shortly after the release of European Vacation, Idle and Chase began work on a screenplay for a follow-up called "National Lampoon's Australian Vacation." Aside from a few shark-related gags, neither could come up with much, and the project was shelved.
Ellen calls Clark "Sparky" in all four Vacation movies. In the DVD commentary for this movie, Chevy Chase said that the nickname was Beverly D'Angelo's idea, and she still affectionately calls him Sparky.
In the DVD commentary, Chevy Chase mentions that as of 2002 he still has several items from this movie, including the complete "Pig In A Poke" pig costume and the Walley World sweatshirt he wears throughout the movie.
The first time Clark hits Eric Idle's character with his car, Idle shrugs it off as being "Just a flesh wound." A similar remark is also made by the Black Knight after sustaining a serious injury in Monty Python and the Holy Grail (1975) also featuring Idle.
Although he is credited as one of the writers of the film (as well as for the characters), John Hughes was not involved with this film. In fact, he had no idea they were coming out with a new Vacation film until he saw a preview of it on TV.
Clark can be seen wearing a t-shirt from "Walley World", the Griswolds' destination in the first film, National Lampoon's Vacation (1983), in the scene set in Chicago where he films Ellen in the shower. Later, while the family is in Paris, Rusty is wearing a "Walley World" sweatshirt in the restaurant scene.
In the closing credits montage, there is a painting of Clint Eastwood, which originally appeared on the movie poster (as well as VHS/DVD covers) from Pale Rider (1985), which was shown in theaters the same year as this movie.
In Germany, Rusty meets a blonde woman, who, while making out with her, shows him her bare breasts. In reality, Jason Lively was 17 and Claudia Neidig was 24. Filming that scene in America may have been illegal.
The car the Griswald's drive on the Continent is a Citroen DS that has been modified - aka the Family Truckster from the first movie - with custom mirrors and add-on scoops over both the front and rear wheels.