When Hogan blows up the Gestapo officer's car to allow Svenson and Magda to escape, Magda is wearing heels. However, when they run into the barracks and get into the escape tunnel, Magda is now wearing flats.
When Magda takes the flowers out of the box, the note is up near the flowers themselves. The view changes and the note is now down in the wrapping.
A warning posted on the prisoners' barracks has VERBOTEN at the top in very large letters. At the bottom, it says "Brussels December 13, 1944". Brussels was recaptured by the Allies on September 3, 1944.
In some scenes, Karl Svenson's last name is pronounced 'Swenson', in others it is pronounced 'Svenson' - mainly by the prisoners. Klink and Burkhalter mainly use 'Swenson'. This shows that the character's name was changed from 'Swenson' to 'Svenson' (the name in the credits) during filming.
When Schultz falls asleep in his chair, Hogan and LeBeau cover his ears with a pair of gloves held in place by an all-wire coat hanger. The hanger used is of a type that had not been invented until after World War II, during which wooden-shouldered hangers (with wire rail-hooks) were still exclusively in use.
The candles on the table at the Hofbrau are citronella patio candles; glass globes with a plastic mesh stretched over them as a decorative accent. These were quite common in the 1960s, but this type of plastic had not yet been developed for such use in the 1940s.
The singer, Magda, wants to marry Swenson, but she is seen wearing a wedding ring while on stage singing.