1. Happy Birthday! = I feel obligated to wish you a happy birthday. Or we're talking on Gchat right now, and this is just a formality.
2. HBD! = I don't really care about your birthday, but I do think something bad will happen to me if I don't wish everyone a Happy Birthday on Facebook, and so I'm just trying to get in and out as fast as possible.
3. Happy Birthday, [your name]! = I feel bad about just saying "Happy Birthday!" but I can't think of anything else to say to you.
4. Happy B-day! = I feel bad just saying "Happy Birthday!", so I'm hoping you think that putting "b-day" instead of birthday means that I put some personality into this.
5. HAPPY BIRTHDAY! = I straight up forgot all about you until Facebook told me today was your birthday. But I am so glad to remember that you are still alive!
6. Happy Birthday! Here is a list of everything I know about you! = I am your best friend. Me. No one else. So I am leaving a list of our most personal and embarrassing stories as a warning to others who might try to take you from me.
7. Happy Birthday, yo. = We fucked at one point, and it's still weird.
8. Happy Birthday, sexy! = We will never fuck, but we're close enough where we can touch each other's butts with impunity.
9. Happy Birthday. = I am really mad at you, and this is the Facebook birthday greeting version of air kisses.
10. Happy Birthday, I miss you! = I probably do miss you, but I think we'd both agree that calling you on the phone at this point would be awkward.
11. Happy Birthday, I MISS YOU!!!! = You do not miss me.
12. Happy Birthday, I miss doing this one thing with you! = You've stopped returning my texts, so I'm hoping that this will come off as a non-creepy away to initiate contact with you.
13. Happy Barfday! = I'm hilarious.
14. A number of years ago, this amazing and beautiful person was born. That person was you! = I'm your mother, and this is basically the only way to get you to acknowledge me on Facebook.
15. Happy Birthday!!!!!!!!!!!!!!!! = I'm a relative who wishes you would call.
16. Happy Birthday! I still remember this one thing that happened! = We are probably not friends anymore, but unfriending you on Facebook just seems kind of mean.
17. Happy Birthday! See you at your party! = Jesus crap I am so glad that I finally got invited to a party you have no idea I'm gonna show up fifteen minutes early and make it really uncomfortable for you.
18. Happy Birthday! It was great to see you the other day! = We ran into each other on accident, so I'm using this to parlay my way into making plans with you.
19. Happy Belated Birthday! = I just noticed that enough of our mutual friends wished you a happy birthday, so if I don't do it now, I will look like a jerk.
20. Ack! I'm so sorry I missed your birthday! Hope it was good! = I hate myself and everything I do is wrong. Or I'm a forgetful asshole who is trying to manipulate you into liking me. OR IS IT BOTH?!
21. Happy Birthday! Hope you have a great day! = I don't really know you, but my birthday is coming up, and I'm trying to make sure that my Facebook wall doesn't look like a ghost town that day because holy crap would that be depressing.