My father is a photographer and so my sister and I were models for stock photography. I was on shopping bags in Mexico, my sister was in a bank brochure. My favorite though is when my sister's high school science class was reading from a textbook an she sees a picture of me, putting mascara on in a mirror. She yelled out to the class, "Hey that's my sister!" Apparently it gave everyone a good laugh.
On a less funny note, I was a kinda chubby kid so my dad did a whole shoot of me in a grey tracksuit looking sad on a scale, and pinching my belly fat in the mirror....etc....ended up on being used in a child obesity campaign. He didn't tell me what it was used in until years later.