Since BD and I were never married, DS has my last name. When DH and I married, I kept my last name.
Anyway, we were at the Dentist and I was updating our insurance. DS used to be on my father's insurance (he had awesome insurance that allowed grandkids to be on it if they were living in the household, and I moved back in with them when I had DS since I was a single mother, and stayed there until DH and I married.)
So the receptionist walks up to me and was asking about the new insurance, and she was confused since the old insurance had the insurance policy holder, parent, and patient all having the same last name, and the new insurance had the policy holder having a different last name. She thought my father was my XH (ha), and wasn't understanding why we were switching insurance. It took me awhile to explain it to her as she just wasn't getting it.
You would think that in today's day and age with so many BFs, different last names wouldn't be such an issue..

Re: Just something funny
That was my thought. When I filled out the form it asked for DS's relationship to the policy holder, and I put "SF." When I filled out the form the first time DS went and he was on my father's insurance, I put "Grandfather." She could have just looked it up if she really cared.
We have 3 different last names in my house. My oldest DD has her father's last name, my younger daughter has her father's (my DH) last name, and I still haven't changed my last name (not sure I will, actually).
We're all on DH's insurance, so his name is on the cards. The first time I took the girls to appointments at their new pediatrician, we confused the receptionist quite a bit lol.
"Man, be creative. Like the stuff you do. Do nice things. Love respectfully. Laugh a fucking lot. Curse when you feel like it. Life is cool." - Jean Grae