According to the book "Spies and Sleuths: Mystery, Spy and Suspense Films on Videocassette" (1988), the filmmakers were forbidden to enter the then official borderline between East Germany and West Germany, a zone which was located about ten feet in front of the Berlin Wall. As such, "because the production was not allowed to cross into East Berlin, an exact replica of the wall from the eastern point of view had to be built just a few feet in front of the west side".
When the punks, including Jonathan in disguise, show their passports to the DDR officer, you can glance at their photos for an instant. Watching the movie on DVD, the still reveals the actors' real names and dates & places of their births. Obviously the actors playing the punks (and also Anthony Edwards) had been told to bring their own passports and show them into the camera.
The names of the two books by Ernest Hemingway that Jonathan Moore (Anthony Edwards) was carrying with him and reading whilst traveling in Europe were "A Moveable Feast" and "Fiesta", the latter which is also known as "The Sun Also Rises". Both books have connections with the film's story. The first book is set in Paris which is also where Jonathan and Manolo visit in the film, the book being a set of memoirs of Hemingway's time there as a youth in his 20s, a similar age to these two young men. The latter is a novel about American and British expatriates who travel from Paris to Spain. This is the same European tour schedule of Manolo and Jonathan in the movie.
The real-life distinctive period structure where a chase and action sequence occurs late in the movie was "The Spandau Citadel", but referred only in the film by its German name, which is the "Zitadelle Spandau". Shooting actually took place there in the real location. The fortress is one of the best preserved European Renaissance military buildings. The medieval fort was built on an island between the Spree and Havel rivers around 1559-1594. It was constructed to protect the town of Spandau and today is a museum and tourist destination.
In the scene set in the veterinary class one of the student extras is wearing a red sweatshirt with the letters "AB" on it in white. This shirt is borrowed from Les Tronches (1984) starring Anthony Edwards and directed by Jeff Kanew, who directed Edwards in this movie. This shirt was worn by the "Alpha Betas," the enemy fraternity of Edwards's Tri-Lams, in the "Nerds" movies.