I say “thankee sai” and punch myself in the throat. But only if the person wishing me well is female.
“Saying it don’t mean shit. Where’s my present, dammit?”
I just thank people on the rare cases it comes up.
Thanking them for the reminder would work too but might confuse most people. 
It just isn’t a day that has worked for normal celebrations for most of my adult life so I don’t pay huge amounts of attention to it myself.
I say “Thank you.”
It’s also what I say to gentiles who wish me “Happy Hanukkah,” or “Happy [insert Jewish holiday/festival].”
It ain’t gonna be happy until you buy me a drink.
‘Thank you’ is right because ‘Happy Birthday’ is essentially a contraction of ‘I hope you have a happy birthday’. It’s an explicit wish for you to be happy today (expressed in a slightly formulaic way). So you should feel no more oddness in saying thanks than you would if they’d said ‘I hope you get to enjoy yourself today’ or ‘I hope your SO is taking you somewhere nice for dinner.’
Do ya.
But yeah, my response is generally something like “Thanks! I’m doing X for my birthday; looking forward to it.” Or something else that lubes conversation in the spirit intended.
Long days and pleasant nights.
In Japanese one congratulates you on your birthday. Why? Maybe because you didn’t die? The proper adult response is to say “Oh no” or “Oh no, but thanks.”
That’s expressly forbidden in Japanese culture, as would agreeing with them.
Yes, ‘thank you’ works for me. Plus I smile at the well-wisher. 
If you would kindly explain, which aspect is “expressly” forbidden in Japanese? I’m not quite understanding. Are you saying that it is more polite to disagree with the well-wishing than to simply acknowledge it, or…?
I apologize for my ignorance here.
“Actually, birthday celebration is against my religion.”
“Oh, sorry. So . . . You’re a Mormon, then?”
“No, an old atheist.”
This is why “you too” is NOT an inappropriate response. I want others to enjoy themselves on my birthday. What, I should want them to be miserable on my birthday? That’s a recipe for getting them to dread and even resent my birthday coming around.
If it is in fact my birthday, “thank you”
If it’s not, it’s “You watched Frosty The Snowman again, didn’t you?”
“I was hoping nobody’d notice.”
… soooo… you’re using l’havdil to separate dog and wife? To clarify that you do not consider them equivalent? (Trying to make sure I understood correctly)
Your quote was missing the relevant bit. Disagreeing that your wife is pretty could send you to sleep with the dog. Agreeing may seem like you’re congratulating yourself on something which is actually no merit of yours.
You say true and I say thank ya
How do you reply when someone says "Happy Birthday"
Thanks for reminding me I’m another year closer to death, ass-hat!
How do you reply when someone says "Happy Birthday"
I was trying to forget. Now I’ll be over here in my corner crying. Thanks, asshole!
How do you reply when someone says "Happy Birthday"
Grab crotch and say, “I loved your mom’s birthday present”.
ETA: “hey, stop crying, Sis, I was kidding”.
Cheers!