One of the reasons I generally DON’T wish people a happy birthday on Facebook is that it’s a struggle coming up with something good, especially in public. If I’m the first or even second or third person, I feel good with “Happy birthday!” If there are twelve “Happy birthday!”s already, plus a bunch of witty remarks, I sit there thinking for too long, then feel like I tried too hard. If I DO come up with something good, it’s hard to re-use it publicly for someone else’s birthday: if I’d put it in an email, no one would have known I used the same cute/clever line for everyone. Not that I do that.
I thought I would compile a list of how OTHER people solved this problem:
“Happy birthday!” The classic. Upside: no one thinks you’re trying too hard.
“Happy birthday!” + intensifier. Examples: “Happy happy happy birthday!” “HAPPY BIRTHDAY!!!!!!!”
“Happy birthday!” + fancier. Examples: “Happiest of birthdays!” “A very happy birthday to you!” “HaPpY BiRtHdAy!~*~!”
“Happy birthday!” + sillier. Example: “Happy cake-and-presents day!” “Herpy berfderf!” “Happy Bmas!” “What the haps, homebirth!”
“Happy birthday!” + sticker or other birthday-card-type picture. This is one of my new favorites. It’s DECORATIVE, but I don’t have to think of something clever. Example:

“Happy birthday!” + name/nickname/endearment. Examples: “Happy birthday, Margaret!” “Happy birthday, sunshine!” “Happy birthday, Bundlebuns!”
“Happy birthday!” + instruction/wish regarding enjoyment of day. Examples: “Happy birthday! Have fun today!” “Happy birthday! Hope it’s great!”
“Happy birthday!” + instruction for specific suggested celebration technique. Examples: “Happy birthday! EAT CAKE!!” “Happy birthday! PARRRRRRRTAY!!” “Happy birthday! WINE TIME!”
“Happy birthday!” + compliment. Examples: “Happy birthday, pretty lady!” “Happy birthday, sweet friend!” “Happy birthday, hottttie!” “Happy birthday! You’re wonderful!”
“Happy birthday!” + affection. Example: “Happy birthday! I love you!” “Happy birthday! I’m glad you were born!”
“Happy birthday!” + teasing. Example: “Happy birthday to you and your manly beard!” “Happy birthday! Where’s the usual selfie??”
Joking reference to age, flattering/neutral. Examples: “Happy 29th birthday!” “Congratulations on the 13th anniversary of your 29th birthday!”
Joking reference to age, unflattering. Examples: “Happy birthday, old man!” “Happy birthday! Don’t light the house on fire with all those candles!”
“Happy birthday!” + apparent reference to in-joke. Examples: “Happy birthday! Don’t forget that elephant!” “Happy birthday! Hope it’s flurbastic!”
“Happy birthday!” + nostalgia. Examples: “Happy birthday! I can’t believe my baby girl is 28!” “Happy birthday! I remember when you were born! What a wonderful day!”
Pretending to sing. Example: “Happy birthday to you! / Happy birthday to you! / Happy birthday, dear [name], / Happy birthday to you!”
Piling it on. Example: “HAPPY BIRTHDAY, beautiful wonderful friend!!! ~*~*~ Have an AWESOME day, you DESERVE IT!!! Eat lots of cake! Have fun! I LOVE YOU!!!! xoxoxo”
And of course there are tons of triple combinations: “Happy birthday! Have a great day! I love you!” and “Happy 29th birthday, Margaret! Always remember the PALamo!!” “Hey, beautiful, it’s your birthday!! EAT CAKE!” In fact, now that I’ve listed it out, I don’t know what my problem is: this is not so hard.