I have several best friends, but my Jayann-pants has become part of the family because she's been my best friend for so long. No really, she just visited my parents and sister when I wasn't even there.
I've known her since I was 12. Her friend Leah was my science lab partner and I met her through Leah. I'm 30 now, so she has been my best friend for 18 years. Our friendship is now a legal adult. It's awesome :D