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.
At the US box office, the film notably knocked Volver al futuro (1985) off the top spot, which it had held for the previous three weeks. Back to the Future (1985) would regain the top spot for the next eight weeks.
In an interview, Chevy Chase said that after this film was released, he got dozens of letters from people who had visited London and ended up trapped in a roundabout.
Dana Hill had Type 1 diabetes, which made shooting Audrey's nightmare scene difficult. Hill had to be very careful to avoid swallowing any of the food she was supposed to be eating.