The sign over the club Elvis played in is misspelled Willkommen and Montag.
The club in which Elvis and his buddy got into a fight was a German club in Germany but the sign over the entrance of the club misspelled two German words: "willkommen" (welcome) and "Montag" (Monday).
Guard for STASI archive is equipped with a East German era AK-47 instead the modern NATO equivalent.
At the end as George plays the guitar for Nigel, it's clear that the notes he is picking do not match up with the dubbed-in guitar part. It's surprising that the editor and/or director chose to show a close-up of George's right hand during this interlude as it only makes the mismatch far more obvious.
Gunther says "da" in identifying himself. A German would say "ja" which is German rather than "da" which is Russian.
Mr. Wilkinson, the Elvis Presley impersonator, said Presley's first appearance on The Ed Sullivan Show (1948) was in April of 1953. Presley's first appearance was not until September 9th, 1956 (his first of three appearances). By this time, Presley had already appeared on The Milton Berle Show (1948) twice and The Steve Allen Plymouth Show (1956).
Cultural Attaché stationed in Germany couldn't pronounce "Schlange" correctly.