In Vienna, Jesse talks about his obsessive relationship with "Miss July, 1978" of Playboy magazine, then asks Celine if she knows Crystal. Playboy's Miss July 1978 was actually Karen Morton, cousin of 1970s model Elaine Morton.
Jesse and Celine are said to come from Budapest to Vienna, but in the train scene, there are forest and hills to be seen outside the window all the time. But there is no such landscape along the railway between Budapest and Vienna. In fact, the landscape looks more like the railway line west of Vienna, in the direction of Salzburg. This suggests that the movie was rather filmed there.
At the club where two guys (director cameo) and two girls are playing foosball, on the girls' side no one is holding the control knob for their goalkeeper. In fact the girls are shoved with one row to the right in order to be their opponents better visible.