The story is loosely based on the last two years of Vladimir Lenin's life, living in a controlled environment similar to what is portrayed in the film. With the justification that over-excitement might cause Lenin health problems, Joseph Stalin had printed for him one-copy edition newspapers, censored of all news about the political struggles of the time.
CGI was used extensively to "de-Westernize" Berlin. Even though it's mostly shot in the former East Berlin and much of the film takes place after the fall of the wall, it's been Westernized since at a furious rate. Many ads for Western products had to be removed, and many colors had to be lightened or grayed significantly.
Sigmund Jähn gave permission to be featured in the movie, but refused to play himself. It was very difficult to find an actor who looked like Jähn and spoke his typical dialect but after filming had begun, Wolfgang Becker chose Swiss actor Stefan Walz. He was given complex make-up and was dubbed by another actor who came from Jähn's home region, the Vogtland.
The reason Denis (Florian Lukas) is seen wearing a T-shirt that resembles the computer code from The Matrix (1999) is because there was initially a scene where he talked about a movie idea of his called "Planet of the Forgotten" which bore a striking resemblance to the plot of The Matrix (1999). This scene can be viewed in the deleted scenes of the DVD.
At the birthday party when Rainer (Alexander Beyer) tries to hide from Christiane his West German origin, he almost says he was a Gauleiter in the children's Pioneer movement. A Gauleiter was the name given to a regional Nazi party leader.