“But you’re too pretty/feminine/straight to be a lesbian.”
“Why would you be a lesbian, you’re pretty enough to find a man.”
“Which one of you is the man?” (to femme couples)
“Can I watch / join you?” (to femme couples from straight men)
“You’ve obviously not had a real man yet, five minutes with me will straighten you out.”
“Are you straight / bisexual?”