When my dad asked me how old I was I said 25 jokingly -- he got so confused there for a second and said, "What? No, you're kidding." We both laughed, but I realize I shouldn't have done that to the poor man -- since his stroke back in June he's had some memory problems. Still, I know he was laughing at himself as well for having to remember.
I then told him I'm celebrating the 20th anniversary of turning 25.