I have a huge famly and so does FI and we wanted a small wedding so we really, really cut on inviting friends. It hurt but it was for the best. As a result, very few of my high school friends got invites. Only 4, actually. if I was having a big wedding, I'd have invited several more, but just couldn't. The 4 that made the cut are my 4 best friends in the world (even though we've been out of school for almost 15 years).
So, I invited any of my single friends/family as "and guest" (there were very few of these, most of my friends/family are paired off). Originally one of the HS friends was bringing a boyfriend. They broke up a month or so ago and she asked if she still had a plus one invite. I said of course. Got her RSVP for 2. Today she texts me and wants to know if she gave her her guest's name. I said no, no biggie, we aren't doing escort cards (FI doesn't want seating chart/escort cards and it wasn't worth the fight for 75 guests). then I asked what his name was, just out of curiousity.
She is bringing one of my best friends from middle school! He and I drifted apart after HS and have only seen each other once since then but he is super excited to be coming to my wedding and I am so thrilled to have him as a guest!
I hope it doesn't sound like he's B-list or something- he's not. My friends and I aren't petty like that. My friend wanted to bring a friend and just thought she'd bring someone that actually knew me who would want to go to my wedding, rather than a stranger who would be bored not knowing anyone there. I'm so excited that he'll be a guest that I wish I had just invited him, now!

When you realize you want to spend the rest of your life with somebody, you want the rest of your life to start as soon as possible. ~Nora Ephron, When Harry Met Sally