So it's a character's birthday. They hoped that others would notice. They have known each other for quite a while, how could they forget?
Oh wait, they did forget. Even if the birthday person reminded them, it's all for naught. It may take a bit for the companions to get over the guilt, while the birthday person is guaranteed not to take it well.
Compare Doesn't Know Their Own Birthday for when they don't know their birthday in the first place, and Forgotten Anniversary for the wedding day variant. If the birthday wasn't truly forgotten after all, and the other characters threw a Surprise Party, it's a Not-So-Forgotten Birthday. If everyone knew about the birthday and it had been forgotten by the one who's celebrating it, then it's Forgot Their Own Birthday. Can lead to a One-Person Birthday Party or Convenience Store Gift Shopping. The opposite of Celebration Miscalculation, which can cover when a birthday is celebrated, but on the wrong day. If they're not invited to someone else's party, it's Uninvited to the Party.
- In the dub of S1E7 of Bakuten Shoot Beyblade, Takao is so excited about his match with Kai that he forgets about his own thirteenth birthday. Luckily, his grandfather hasn't and whips him up a party. This is a departure from the original, in which the party being thrown is a pre-battle encouragement attempt. Plus, Takao is ten.
- An omake of Bleach reveals that Urahara's and Yoruichi's birthdays are forgotten every year and they have to celebrate them alone (although together). The reason for this is because their birthdays are December 31 and January 1.
- IGPX: Occurs completely by the book in an early episode to Amy, who has had workaholic parents her entire life and only recently made friends with the members of the team. Her (absent) parents actually do forget her birthday.
- In episode 13 of My Love Story!! it's Suna's birthday but it turns out he forgot it himself. He didn't understand why his friends were acting so overly attentive towards him.
- One Kalos episode of Pokémon reveals that Jessie's teammates, James and Meowth, forgot her recent birthday. Only her Pumpkaboo remembered it. This is even more noticeable because the anime completely avoids characters aging.
- In one episode of Sailor Moon S it's Usagi's birthday and when she drops an unsubtle hint about what she wants for a gift, Mamoru reveals that he didn't know it was her birthday so he gets a huge slap in the face from her. Turns out she never actually told him when her birthday was. Even worse, she doesn't know his birthday either.
- On Yuki Yuna is a Hero, Karin had forgotten her own birthday, which she had never had a real celebration for before, and was thus surprised when the others show up to throw her a small party.
- In one Archie Comics story, Reggie Mantle's birthday is coming up. He overhears the gang wondering what to do for 'the most important man in town' and the egotistical Reggie assumes they're talking about him. Reggie nudges the gang into arranging a banquet at a fancy club...and it turns out that the gang was talking about an old war veteran who was born in Riverdale. And Reggie's the only one there who isn't in his golden years.
- In Avengers Undercover, Nico completely forgets Molly's birthday because she's still struggling with PTSD.
- In one Donald Duck comic, Daisy Duck forgot her own birthday.
- Robin Series: Tim Drake's parents along with his girlfriend Stephanie and friend Ives are able to give him a surprise party for his sixteenth when his step-mother realized he had forgotten his own birthday. Earlier he had managed to forget Ive's sixteenth birthday so Ives found it particularly funny. Tim was also surprised by Ives' fourteenth and fifteenth birthdays but Ives ensured he didn't miss those ones.
- Guys Being Dudes: Spark doesn't usually celebrate his birthday because it falls during Go Fest preparation season.
- The Amazing Spiderman 2: Max (the guy who will become Electro) has his birthday in the day we first see him. But nobody (in his workplace) seems to remember, or care, about it. He even is told to repair the building's electrical system the same day. He also throws a One-Person Birthday Party.
- The Assistant: Jane forgets her father's birthday. He is very sweet about it and tells her he doesn't mind because he knows how busy she is.
- In The Deep Blue Sea, Rachel Weisz' character attempts suicide after her beau forgets hers.
- At the start of High Lifes and Low Lifes, Shannon comes home from a 13 hour shift at the hospital expecting her boyfriend Ray to rake her out for her birthday dinner. He has totally forgotten, and when she tries to get him at least take her out for a drink, he is not interested. Instead, she decides to go out with her best friend Frances, kicking off the plot.
- In Jaane Tu... Ya Jaane Na, Aditi's birthday is missed by her best guy friend for a date with Mehgan. She doesn't take it well.
- A weird subversion in Overboard; Dean tells Joanna he's forgotten her birthday as a substitute confession. He was really about to tell her how she's actually an amnesiac heiress who he tricked into believing she's his wife, but he chickens out at the last second.
- In Sixteen Candles, the main character's birthday is forgotten by everyone due to the furor caused by her sister's impending (and last minute) wedding. Except for her younger brother. He deliberately ignored her birthday because he's a jerk.
- In Troop Beverly Hills, troop member Chica ends up at Troop Leader Phyllis house because her parents took a last minute trip to Monaco leaving her alone on her birthday. Phylliss maid Rosa makes her a Mexican food dish decorated with candles and the household sings Happy Birthday to her.
- In Wild Bill, the title character has been away in prison for eight years when he's forced to live with his two children (whose mother has abandoned them). One of his first days back happens to be the older son's sixteenth birthday, which he forgets; he tries to make up for it, but his choice of gift merely sets him off.
Bill: No, I felt bad about missing your birthday.
Dean: Which one?
- In Animorphs, Tobias (who is Shapeshifter Mode Locked as a hawk except for two-hour intervals) learns that he is supposed to meet with a lawyer to receive a letter from his biological father on his "next birthday." He is a bit embarrassed to admit that, like other aspects of his human life, he can't quite remember when it is.
- In one of the Gossip Girl books, Eleanor Waldorf unwittingly schedules her wedding for Blair's birthday.
- In The Great Gatsby, we have the big scene where all the secrets between Gatsby, Daisy and Tom are revealed. Afterwords, First-Person Peripheral Narrator Nick suddenly realizes that it's his thirtieth birthday, which, combined with the aforementioned drama, spurs on a low-key midlife crisis.
- Harry Potter has the Dursleys generally forget his birthday. In Chamber of Secrets, Dudley mocks Harry about it being his birthday and how his friends seem to have forgotten about it, since nothing has arrived for Harry in the (owl) post. Uncle Vernon and Aunt Petunia do seem to have forgotten about it, or are ignoring it, as they are too focused on Vernon's boss coming over for dinner and hoping to make a good impression.
- Spy School: Murray Hill forgets his partner-in-crime Dane's birthday every year, even though their birthdays are on the same day.
- In one chapter of Winnie the Pooh, Pooh noticed that Eeyore seemed very depressed (more so than usual), only to find out no one took notice of his birthday.
- In the Aly & A.J. song "Potential Breakup Song" the singer's boyfriend forgot her birthday.
It took too long for you to call back/And normally I would just forget that/Except for the fact it was my birthday/My stupid birthday
(...) What kind of a boyfriend would forget that/Who would forget that?
- The Birthday episode of You Don't Know Jack: Louder! Faster! Funnier! features everyone forgetting Schmitty's birthday. Despite trying to act like it's not a big deal, Schmitty is very clearly upset by the whole thing, including replacing an instance of "my father" with "my father, who didn't bother sending a card!"
- Amnesia: Memories' fandisc Amnesia LATER: Ikki points out that Kent doesn't care much for his birthday and often forgets the importance of the date. When the heroine asks Kent to come over to her place on the 23rd under the pretense of just having a relaxing date watching movies, she's surprised to learn that he really doesn't associate that date with his birthday.
- In Bravest Warriors Danny built a Robo-Chris to make Chris jealous because he forgot Danny's birthday.
- Because I'm Depressed has a story arc where Diego forgets his own daughter's birthday, and has to beg for Eve's help to keep Chel from finding out.
- Haru from Cross Heart is so sullen due to her Long-Distance Relationship that she barely takes notice of her birthday anymore. Her friend has to remind her.
- Far Out There ran a page in which Jenna's birthday is forgotten after the author realized he had forgotten the COMIC'S birthday.
- StacheBros: In "Mario & Luigi! Stache Bros - The Stachey Sequel", the only people who even remotely seem to care about Waluigi's birthday are the Mario Bros., but they don't even attend his birthday party and only get him some bubble wrap as a gift. When Waluigi is introduced, he's depressed that no one even bothered to celebrate his birthday.