Major Teppel tells the Gestapo that he is late for a meeting with Admiral Canaris. Admiral Wilhelm Canaris was in fact at that time the head of the Abwehr, and like the fictional Teppel was secretly involved in plots against the Nazi regime. Canaris was later executed for treason.
In the hotel lobby, Gestapo officers tell Colonel Hogan that he is to be taken to a General Schellenberg. Presumably, this refers to real-life SS General Walter Schellenberg, head of German foreign intelligence.
Hogan says, "Morrison? You got more guts than a Philadelphia lawyer." Long ago, 'Philadelphia lawyer' meant a lawyer who won because of his incredible encyclopedic knowledge of the law. By 1960 it meant a lawyer who won because of his arrogance, bluster, and shameless dirty tricks.
LeBeau says to Klink in French - "Ça veut dire 'tous les Boches sont des cochons, de parents de cochons, et vous êtes tous les deux un bon exemple de vos ancêtres." (In English: It means "Every Bosch is a pig, of pig parents, and you two are a good example of your ancestry.") - which makes Major Teppel aka Robert J. Morrison to begin smiling, turning aside so Klink can't see him laughing.