Annoying sexist assumptions accepted as general knowledge, aside from the obvious ones about housewives and work status, Japan-specific:
-Men walk faster than women (it's common to see on a map something like: "walking time for men: 15 minutes. walking time for women: 20 minutes").
-Women enjoy cake and sweets and men don't.
-The existence of "ladies' set" meals, lighter and a better deal. Usually, men are NOT PERMITTED to order this set.
-Women drink less than men and so should pay a smaller percentage of the bill when going out for drinking parties.