The girls automatically assume the man is from Germany, because he speaks German as his native language. There is no reason for them to automatically think he is from Germany, because German is the dominating language of Europe and is the native language for twenty-five percent of native Europeans.
After Eric leaves, Laverne goes into the bedroom to change. When she walks by the bathroom, the door is opened wide and you can see the sink. Shirley walks into the bedroom and when they show the bathroom, the door is only partially.
Laverne refers to Lenny and Squiggy as dorks. However, this episode is set in 1958-1959, and the term "dork" did not come into use until 1961.