An Ironic Birthday occurs when a character has had to make a tough decision or has just lost something of extreme value to him, and upon walking into a room is greeted with a surprise birthday party. This is not a celebration that makes everything all right; this is about the character having to pretend to enjoy what should be a happy time while secretly suffering. He's grateful to his friends, but a party is the last thing he needs.
Contrast One-Person Birthday Party (when the character is suffering because nobody showed up to their party) and Forgotten Birthday (when the character is sad only because they don't know about the surprise party.) If their birthday is miserable but they don't have to act cheerful for a party, it's A Birthday, Not a Break.
Also not the victim's birthday: In Mazinkaiser, Baron Ashura infiltrates the Photon Power Laboratory disguised as Professor Yumi, and walks in on Yumi's surprise birthday party. To make matters worse, all the presents remind him of Baron Ashura, including a Baron Ashura-themed dartboard. He dashes out, screaming that he is, in fact, Professor Yumi.
In the Mahou Sensei Negima! anime the girls and Negi throw one for Asuna in episode 23. Because she sold her life to the devil exactly ten years before, she'd known for years that this was her last day alive. She sulks the whole episode until she goes back to a surprise party for her, and she celebrates with them, resulting in a Crowning Moment of Heartwarming. Her death minutes later is the most shocking event of the entire series.
Naruto. He was born on the day his town was attacked by a demon, and the day his parents died, and said demon was the reason they died.
During the big finale final battle, the villain tries to taunt him by pointing out that it happens to be the day before the anniversary of his parents' death (and how pointless their sacrifice was since it's all going to end now). Backfires of course, because Naruto just states that means its also his birthday, and thus the anniversary of his parents' victory by saving their newborn son during the attack.
The Empath: The Luckiest Smurf story "Smurfed Behind: The Departure" takes place around Empath's 155th birthday, when all the Smurfs in the village end up being lost in time, similar to the events that took place in Season 9 of The Smurfs cartoon show. This leaves him coming home to an empty village save for his friend Polaris Psyche.
In the Left Behind book Kingdom Come, Cendrillon Jospin's parents realized that their child would not become a believer by her 100th birthday, which in the Millennial Kingdom period means an automatic death sentence to Hell, so they celebrated her birthday before the day that she would die. She still went to Hell nonetheless.
In Smallville, there has not been a single perfectly happy birthday shown. Lex Luthor's 12th birthday involves an empty party. Clark's 16th birthday was fine for him at the time but Chloe saw him kissing Lana and left crying. He misses his 17th birthday because he is stabbed by an Ax-Crazyteenager withhis powers. His 19th birthday was not long after Jonathan died. Chloe's 18th birthday involves being possessed by a Wicked Witch who proceeded to bloodily torture Clark. Her 22th birthday was after she suffered through a long Trauma Conga Line, and Zatanna had the bright idea to transform her into Lois. And Clark didn't show up for the party.
Frasier, who had two: one where he was trying not to accidentally stand up a woman for the third time, and one where he accidentally (with a little help from Roz) revealed his entire sexual history to the waiting party-throwers.
The first episode of Breaking Bad pretty much revolves around this trope. Walter White comes home from the hospital on his 50th birthday, having just learnt that he has terminal cancer, to find a surprise party in his living room.
A season 5 episode features his 51st birthday (with a lampshade hung on how long a year it's been), celebrated for Walt Jr's sake despite the fact that he and Skyler are barely on speaking terms. The Cold Open to that season shows his 52nd birthday, "celebrated" alone, in a diner, travelling under a fake ID.
In Season 2 of Buffy the Vampire Slayer, Buffy pretends she's okay when her mother (who doesn't know about Angel) celebrates with a movie and a birthday cupcake.
Possibly inverted in the Firefly episode "Out of Gas," where everything goes to hell during a surprise birthday party for Simon.
It is not his birthday, but for B.J., in the M*A*S*H finale, it might as well have been. He had made every attempt to get home in time for his daughter's birthday (he had not seen her since she was an infant). He got a third of the way there before having to turn around and come back to fulfill Potter's request for another surgeon. The 4077th then throws a substitute birthday party for his daughter.
A notorious episode of All in the Family involved Edith Bunker arriving to a surprise birthday party after being attacked by a rapist.
In How I Met Your Mother, Ted wants to fire his former boss Hammond, but events keep getting in the way, including a surprise birthday party for Hammond, and the next day another surprise birthday party for Hammond (many employees having missed the first). This trope's usual effect applies more to Ted than to Hammond, who just seems pleased.
Inverted in the 1993 musical of Tommy: As 4-year-old Tommy, his mother, and her new lover celebrate her 21st birthday, her presumed-dead husband arrives and breaks up by engaging in a fight between him and the boyfriend that soon leaves the boyfriend dead... all the while the mother tries turning Tommy away from the fight toward the mirror... with which he witnesses said fight by looking at it, after which the parents soon get surprised by what they see before the father gets arrested. Whoops!
A reverse version, minus the surprise: The events of The Legend of Zelda: The Wind Waker take place on Link's birthday. He's just received his gifts from Grandma and they're starting to celebrate when his beloved little sister gets abducted by a giant bird.
Harvey Birdman, Attorney at Law plays with this. He is convicted and sentenced in the murder of Dyno-Mutt, goes to jail, goes through his years of appeals, ends up on death row, goes through catharsis and healing experiences as he makes peace with his lot in life, goes to the electric chair and surprise! This was all a set up for his birthday party. Where this becomes a straight example is that the prison marriage to Magilla Gorilla was real.