Mine tended to happen when I was in my early/mid teens. I was quite tall and my dress sense was older (not in an inappropriate way, just plain colours etc). I used to go shopping with my dad a lot as we both had a love of cooking and would get ingredients together then cook with them at home.
I can think of several different occasions where I was mistaken for my dad’s (in his mid-50s during this time) much younger girlfriend.
The first time, I pointed and something and said to dad “Let’s go and have a look at this.” and he followed me. An older woman tutted and said to dad “Well you clearly go where the young girls go.” Dad was in too much shock to correct her, and she buggered off. We often got looks in the shop as well.
Another time at a motorway service station on the way to a holiday. My mum and brother stayed in the car and we went in to get coffees. Friendly barista asked where we were going, and my dad replied ‘Cornwall’. The barista then said “Ah, romantic break?” and my dad corrected him that I was his daughter and it was a family holiday. The barista’s face was a picture.
These incidents eventually made me too insecure to go out just me and my dad, which is a shame. I always wondered how messed up those people’s lives must’ve been to assume something grim like that rather than us just being a father and daughter.