Girlfriend's Father

I had the same problem, but more extreme, with my current wife.
I had age make-up on in the show we were doing. Her parents were unfamiliar with stage and film "tricks" and were convinced that she was dating an old man... it was a week before they could meet me.
It did not get much better though... I had very long hair, a leather jacket, pants, etc, with all the religions represented on the back with the "Immaculate Deception" tagged on the bottom, in graffiti style. Her step-father was a preacher. They found out I was one of her college teachers... she just turned 18. In fact, the first adjunct teacher for the acting class for that college. It was only her second show at that college.
Ahhhh... good times!
I did not date her until after the class BTW, it was her idea, I sent her away three times. I am made of flesh and bone ya' know.