Ironic Birthday

[I'll] pretend I'm okay with it all,
Act like there's nothing wrong.

—Kelly Clarkson, "Masquerade"

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.

Examples of Ironic Birthday include:

Anime and Manga

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.

Film

In Spider-Man 2, Peter just lost his job, and just had a bad day overall, and comes home to a (heartwarmingly pathetic) birthday party.
Not a birthday, but in District 9 Wikus walks into a surprise party to celebrate his promotion as he slowly turns into a alien.
In Amityville 2: The Possession Sonny is trying to hide his Demonic Possession but is surprised to see his family and friends throwing a birthday party for him. He ends up isolating himself from his own party and then succumbs and murders his family after the guests leave that night.

Live-Action TV

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.
Friends
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.
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.

Music

A variation on "just lost something of extreme value": In Lesley Gore's 1963 hit "It's My Party", the singer discovers that her boyfriend has given a ring to another girl — at her birthday party.

Theatre

Pretty much the plot of the Jonathan Larson musical tick, tick... BOOM!.
- In a lesser sense, also Company, one of the Sondheim pieces it's based on.
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!

Video Games

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.

Western Animation

Teen Titans features the extreme example of Raven's friends celebrating her birthday, while she knows it signifies The End of the World as We Know It.
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.