It's my birthday too, yeah!
They say it's your birthday
We're gonna have a good time!
Birthdays. A celebration of the individual and their continued existence on this Earth, a personal and special day for the birthday person, a day all about them. Except that, with only 365-366 days in a year and billions of people on the planet, no birthday is unique to the individual. Everyone shares a birthday with someone... and occasionally, a character may just run into someone else who has the same birthday as them .
Results may vary.
This may be a cause for bonding if the characters decide to celebrate together or, at the very least, realize they have one thing they can both relate to. This may also be a cause for a rivalry or inflame a pre-existing rivalry, as both characters may want the spotlight, and compete to have their party be bigger and better than their enemy's. It may even mean both characters are special somehow if the birthday they share is a Significant Birth Date.
Regardless of the result, though, the fact that these characters have the same birthday is important to the story, not just a one-off gag or a random coincidence. The characters will acknowledge it and actually care about the (usually) coincidental connection they share, even if it's because they hate each other, and can't stand having anything in common.
These characters, of course, should ideally be unrelated. Twins are inherently born on the same day, note so this trope concerns those who aren't twins... that is, unless the point is to foreshadow a Separated at Birth twist, with the characters (and often the audience) not knowing right away. This also means other familial relationships are allowed, assuming the emphasis is on the special shared date just as in a non-related-character example. They also don't have to be literally born on the same day down to the year, so long as they share the same birthday each year they're both alive.
Truth in Television, obviously. Everyone shares their birthday with someone. An interesting thing to note is that, according to the birthday paradox, it only takes 23 people to have a 50% chance of having a pair with the same birthday. In fiction, the fact that this trope is usually averted makes it similar to the One-Steve Limit. Even though it's common in real life, unless it has some sort of significance to the story, it would be weird for two characters to share the same name, just as it would be weird for them to have the same birthday.
Compare Perennially Overshadowed Birthday for when a character expresses frustration, anger, and/or sadness at having a birthday on the same day as a holiday or annual event and it being consistently overlooked or downplayed.
- Played With in Blue Exorcist (anime only). When Izumo discovers that the class is throwing her a birthday party, she gets annoyed, insisting that since they haven't had one for anyone else, this party will celebrate everyone's birthday.
- In The Cherry Project, Chieri and her love interest share the same birthday.
- In City Hunter, Miki and Kasumi discover that they share the same birthday shortly after Kasumi starts working at Cat's Eye Cafe, which Miki has been working at since it was founded during a previous Story Arc some time ago. After they make this discovery, they plan to hold a birthday party for themselves, which is the start of an upcoming Story Arc.
- Invoked, kind of, in Eden of the East. The series opens with the protagonist getting amnesia and meeting his Love Interest; he borrows her jacket, accidentally taking her ID in the process. When he gets back to his apartment, he finds a large collection of passports with his picture on them. Unsure which, if any, is his real identity, he picks one whose birthday happens to be one day apart from the love interest's.
- Full Metal Panic!: Though not mentioned until well into the series, all of the Whispered around the world were born on within the same three-minute timespan (though local time frames mean some are on different calendar days).
- In Hitoribocchi no OO Seikatsu:, Bocchi Hitori and Kai Yawara discovered they shared the same birthday at age 5. Kai was upset that Bocchi kept calling her "Yawara-San" and refused to let her leave until she called Kai by her first name. When Bocchi explained the next day that she didn't use Kai's name because she wanted Kai to stay with her, Kai promised to stay with her and that they would always celebrate their birthdays together. Kai was Bocchi's Only Friend from this point until the start of the series.
- Kaguya-sama: Love Is War:
- Fujiwara and Ishigami were both born on Hinamatsuri (March 3rd). Fujiwara immediately begins complaining upon hearing this because she doesn't want to have to share her birthday party. When their birthday is celebrated later in the series, Fujiwara spends the whole time whining.
- Kaguya and her Shadow Archetype/cousin Maki (and by extension Maki's twin brother Mikado) were born on New Year's Day.
- In Laid-Back Camp, Nadeshiko Kagamihara and Aoi "Inuko" Inuyama are both pleasantly surprised to find that they share a birthday on March 4.
- Tegami Bachi: Letter Bee: Lag and Sylvette are both born on the Day of Flicker. Being born on the Day of Flicker caused Sylvette's legs to be non-functional from birth, while Lag has an eye missing. As one may guess, the Day of Flicker later turns out to have been a sign of something bigger going on.
- Strike Witches: The protagonist, Yoshika, shares her birthday (August 18) with another member of 501st Joint Fighter Wing, Sanya, who is an exact year younger. The anime later introduces another girl, Shizuka, who also happens to share this birthday and is a year younger than Sanya.
- In Asterix, Asterix and Obelix have been friends since day one because they were born on the same day.
- In the Avantasia Protag AU series, there's a chapter where the four main characters realize none of them know or celebrate their birthdays. They then decide to celebrate them all together as a family on the same day.
- In Unexpected Surprise, Emma and Gabriel first meet when the little girl leaves her mom's office to cheer someone up during her birthday, and runs into the boss grieving because it's also the birthday of his beloved late wife.
- In Incorrect Smash Bros Quotes, Galeem and Dharkon share December 7th (the release date of Super Smash Bros. Ultimate, their debut game) as their birthday.
- 16 Wishes: Abby and her next-door neighbor rival Krista share a birthday. This is torturous for Abby, who is stuck watching Krista get huge parties, expensive gifts, and even a lot more respect from the adults than she gets. The plot is that Abby wants to have the best Sweet Sixteen ever, and uses a bunch of her wishes to knock Krista down a peg at the same time. This then ties into the reason why Krista bullies Abby: Abby stole Krista's best friend, Jay, from her during a birthday party, and Krista hated her ever since.
- In Identity, the characters slowly begin to realize that something eerie is going on when they discover they all have the same birthday.
- Happy Death Day: Tree and her mother shared the same birthday; as she explained to Carter, this was part of the reason they were so close, and her death is also the reason Tree dislikes and tries to ignore her birthday in the present.
- Neville Longbottom and Harry Potter of Harry Potter fame were actually born a day apart,note but this turns out to be an incredibly Significant Birth Date since the Chosen One prophecy specified that "the one with the power to vanquish the Dark Lord will be born as the seventh month dies." Voldemort took that to mean Harry, but Neville also fits the criteria and could have ended up as The Boy Who Lived had Voldemort made a different choice.
- In The Lord of the Rings, Bilbo and Frodo share a birthday, September 22. The story opens with their shared birthday party (Bilbo's 111th, Frodo's 33rd). After Bilbo leaves the Shire to go adventuring again, Frodo continues to refer to the date as "our birthday" and keeps up the tradition of joint birthday parties.
- Monster of the Year: Michael and Kevver first started sitting together at lunch in first grade because they both had Frankenstein lunchboxes. Discovering they shared a birthdate (August 29) is what cemented their friendship, and they've been close as brothers ever since.
- The first Septimus Heap book opens with Septimus and Jenna both being born on the same day. Jenna's mother the Queen is killed, and she's adopted by the Heaps, who have just lost Septimus (they were told he died, but he was actually kidnapped for 11 years).
- In Snow Flower and the Secret Fan, Snow Flower and Lily end up being chosen as each other's laotong in part because they share the same birthday.
- In Something Wicked This Way Comes, Will Halloway and Jim Nightshade have separate birthdays but were born two minutes apart (before and after midnight on October 30th and 31st, respectively).
By their voices, the boys had told the tale all their lives, proud of their mothers, living house next to house, running for the hospital together, bringing sons into the world seconds apart; one light, one dark. There was a history of mutual celebration behind them. Each year Will lit the candles on a single cake at one minute to midnight. Jim, at one minute after, with the last day of the month begun, blew them out.
- In Switch, the second sequel to Savvy, Gypsy is very energetic and happy, but her grandmother, Pat, is a Grumpy Old Woman, and they share a birthday, so Gypsy worries that she will also be grumpy when she's elderly.
- The Big Bang Theory: In "The Birthday Synchronicity", Bernadette goes into labor with her first-born at midnight on Amy's birthday, which interrupts Amy's annual "birthday coitus" with Sheldon.
- Bunk'd: Both Tiffany Chen and Hazel Swearington were born on the same day. This was best exampled in "Boo Boos and Birthdays" when Hazel overhears Emma and Lou's party plans for Tiffany and believes they're for her and they remembered; matter of fact, no one remembers Hazel's birthday anyway.
- Derry Girls: In the series finale, Erin and her cousin Orla's family are too cheap or poor to have separate 18th birthday parties for both of them, so they're combined into one, making Erin wait for three months until Orla turns 18. Then they find out that their parents rented the venue on the same day as the church's First Communion to save money, and then they find out that everyone from school went to Alpha Bitch Jenny Joyce's 18th birthday party instead. Played with, since none of these characters actually share a birthday, but their parties are all happening on the same day.
- Emily Owens, M.D.: Emily's and Cassandra's birthdays happen to be on the very same day. They're young doctors who used to be classmates in high school, Cassandra being the gorgeous popular mean girl who enjoyed tormenting Emily. Now they're interns in the very same hospital and Cassandra still enjoys toying with the very nervous Emily. Emily doesn't really celebrate her day and doesn't want anyone to know, but Cassandra reveals it to everyone, enjoying everyone's attention and Emily's embarrassment. Emily's friend Will forces her to throw an impromptu birthday party in her flat. Emily is also talked into playing the cello for her guests and everyone ends up being impressed with her musical skills. Cassandra on the other hand looks like a sourpuss and is unhappy the party doesn't revolve around her.
- Full House has Becky go into labor with Nicky and Alex at Michelle's birthday party. The episode ends with the entire Tanner family singing "Happy Birthday to You" to all three of them in Becky's hospital room.
- Good Luck Charlie: The Duncans' fifth child, Toby, who was born midway through the third season, shares the same birthday as Charlie three years apart. To call them buddies, however, would be pushing it, as in The Stinger of "Charlie 4, Toby 1", Charlie's birthday wish is for Toby to disappear.
- Played with in the Growing Pains episode "Birth of a Seaver". Maggie goes into labor with Chrissy on Ben's birthday, leaving Ben upset about being ignored until he has a heart-to-heart talk with a dying elderly man in the hospital. But the labor takes so long that by the time Chrissy is finally born, it's past midnight, and Ben is relieved that he won't have to share his birthday with his new sister after all.
- House of Anubis: Joy and Nina were both born on July 7th, which is a Significant Birth Date. Joy was believed to be The Chosen One because of her birthday, but wasn't born at the exact right time; this lead to the reveal that Nina, who had the same birthday, was the real Chosen One, being born at 7:00 AM. The two of them were, incidentally, born 12 hours apart.
- How to Rock: Kacey and Nelson have the same birthday. When their friends plan a joint birthday party, Kacey's diva tendencies end up monopolising the event to her needs only. When she realises what a self-centered jerk she is being, she changes the party to cater to Nelson's interests.
- Liv and Maddie: To encourage bonding between the Polar Opposite Twins Liv and Maddie, their parents told them they were born on the same day, when actually, Maddie was born the day after Liv. When the secret is finally revealed, they chose to keep the tradition going.
- Mike & Molly: In the series finale, as everyone gathers at the hospital for the birth of Mike's and Molly's adoptive child, Samuel quietly mentions that it's his birthday too.
- The New Adventures of Old Christine: In the penultimate episode, New Christine gives birth to her daughter on Old Christine's birthday.
- The Orville: In "All the World is Birthday Cake," Commander Kelly Grayson asks Lieutenant Commander Bortus to have a shared birthday party with her, as they have the same birthday. Later, after visiting a planet where people are divided into castes based on when in the year they were born, the two do share a birthday party.
- Out Matched: Marc and Leila have a shared birthday. When their older siblings deduce that this is impossible due to them being born in summer and winter respectively, their parents admit to artificially engineering the situation. When Leila finds out, she prefers to keep the reassigned birthday because she enjoys a joint party with her brother.
- Power Rangers S.P.D. has a variation where Jack and Syd decide to become Birthday Buddies voluntarily: Jack had grown up on the streets, Never Had a Birthday Party, and doesn't even know when it is; which causes conflict with Syd when he quashes her birthday plans without understanding what the big deal is. When they reconcile, Syd offers to share her birthday with him and he adopts her birthdate as his own.
- All the cluster members in Sense8 were born at roughly the same time in different parts of the world.
- In the Space Cases episode "It's My Birthday, Too, Yeah", Radu lies and claims that he shares a birthday with Bova because his species don't actually have birthdays and he's Never Had a Birthday Party.
- Stuck in the Middle: Louie and Beast have separate birthdays, but did not know this. When Harley informs of them, they also choose to keep sharing a joint birthday.
- In The West Wing episode "Noël," it only further messes with Josh's already traumatized mind to find out that he and the suicidal Air Force pilot, Robert Cano, share the same birthday.
- In the The Wubbulous World of Dr. Seuss episode, "The Birthday Moose", the Birthday Bird takes everyone sharing the same birthday to Katroo for a huge party. In this episode's case, it's Thidwick the Big-Hearted Moose, Morton the Elephant Bird, Fox in Socks, Mr. Knox, and Fiona Phish. When Thidwick finds out that the Birthday Bird is unable to make it this year (due to being frozen alive in a block of ice at an arctic climate), Thidwick tries to take him and his friends sharing the same birthday to Katroo himself, disguised as the Birthday Bird.
- In Spirit of the Century, the player characters are all 'Centurions': 'potent individuals of action', born on the first day of the century, and endowed with extraordinary skills and abilities.
- It's possible for your birthday in Animal Crossing to fall on the same day as a regular villager's birthday. It gets acknowledged as something unique and exciting.
Peppy: I can't believe it's your birthday AND it's my birthday too! This is, like, the best day of the year! Two birthdays, two cakes, and double the presents!
- In Dragon Quest XI, the protagonist and his Childhood Friend Romance Gemma not only share a birthday but they were born on the same day. As the game begins, they must climb a mountain as part of a coming-of-age ceremony, and it's remarked that it's almost unheard of for more than one person to perform the ceremony at once (although Gemma hardly minds having a companion/bodyguard for the trip).
- Elsword: Elsword and Aisha shares the same birthday, in December 27th.
- Fire Emblem: Three Houses: Whatever birthday you put in for Byleth, the mysterious girl in their visions shares as well. She comments on this and feels connected to them because of it. Actually, that birthday only belongs to Sothis. Byleth just osmosed it due to Sharing a Body. Though even once their real birthday is revealed, Byleth's friends still celebrate their birthday on the day you entered.
- Morgan and Amy from Double Homework share not only a birthday, but also a first name (Morgan’s real name is Amy).
- El Goonish Shive: Susan and Diane are near-Identical Strangers (with the only real physical differences being magically induced on Susan's part) who go to different schools in the same town, and who are being watched over by the same immortal. The evidence they might be twins is heightened by the fact that they were born hours apart. Downplayed in that they don't technically share a birthdate (Diane was born before midnight on New Years Eve, while Susan was born after midnight on New Years Day) and full-on subverted when it's revealed Susan's mother definitely only had one kid — their birthdays were a Red Herring for the real reason they look so similar (sharing an immortal ancestor).
- The 8-Bit Drummer shares his birthday with his wife.
- Ayunda Risu of hololive and Oga Aragami of holostars both have their birthdays on January 15, and the two have collaborated to celebrate their shared birthday.
- The Lizzie Bennet Diaries: Lizzie Bennet is very close with her best friend Charlotte Lu, who was born on the very same day as she was. Lizzie jokes that they have been friends since fetuses because their mothers were friends who frequented the very same book club and went to labour at the same time. There's a rumour that Lizzie as a child behaved like a brat during Charlotte's 6th birthday party and wanted to open all of Charlotte's presents. During Q&A with fans, one person said they sensed a lot of drama in that story since it must have been Lizzie's birthday as well. Charlotte snarks that it's precisely it: Lizzie had her own presents to open.
- The reason Critical Role castmates Liam O'Brien and Laura Bailey chose to make their first campaign's characters twins is because they share a birthday though in real life Liam is 5 years older than Laura.
- The Arthur episode "Arthur's Birthday", adapted from a book of the same name, deals with Arthur and his classmate Muffy having their birthday parties on the same day. Arthur and his friends aren't sure whose party to attend until they come up with a solution: they turn it into a surprise party for Muffy at Arthur's house.
- In Avatar: The Last Airbender, it is revealed that the previous Avatar and the Fire Lord that started the war (Roku and Sozin) were actually born the same day, and show that they were very close friends, even celebrating their birthday together. This all contrast with their later relationship as bitter enemies in their old age.
- Ben 10: Cousins Ben and Gwen Tennyson share the same birthday, and since they are both 10 years old that means they were born on the same day. Since they are both spending the summer travelling with their grandfather Max, they get into an argument over whose birthday should be celebrated on the actual date of their birthday.
- This is actually enforced in Captain Star, as crews are assembled with every member having the same birthday as they feel it will help them get along better.
- Subverted in The Fairly OddParents! episode "Boys in the Band", where Timmy is having a miserable Forgotten Birthday alone at home with Vicky while his parents are going to the Chip Skylark concert. Chip Skylark then winds up at Timmy's house, held hostage by Vicky, and it turns out to be his birthday, too. Timmy, having initially blamed Chip for ruining his birthday, starts to bond with him over the fact that they're both having a miserable birthday... except that Timmy's birthday was actually the day after, and it was he who forgot. Although a later special claimed the two did share a birthday, so maybe it was his parents that forgot.
- Another episode has Timmy and Chloe learning they have the same birthday, and both compete with each other to have the better birthday party.
- In Futurama, Cuthbert is a clone, but decides to celebrate his birthday on the day his "father," Professor Farnsworth, extracted the DNA to create him. His best friend Dwight happens to have a birthday the same week, so they decide to throw a joint party. (Nobody shows up except Tinny Tim, who happened to find a discarded invitation.)
- In Infinity Train season four, Ryan and Min-gi's fathers met each other at the hospital nursery when they were born.
- Invoked in Kipo and the Age of Wonderbeasts: When Kipo realizes it's her birthday, she learns her friend Wolf has never celebrated her own birthday and doesn't even know when it is. Kipo decides, from now on, she and Wolf will share a birthday.
- My Little Pony: Friendship is Magic: A twist occurs in "Party of One"; Pinkie Pie's birthday lands one day after the birthday of her pet alligator Gummy.
- The Simpsons:
- The episode "The Springfield Files" reveals Homer shares his birthday with the family dog, Santa's Little Helper. However, due to the Alien Episode plot that Homer is trying to prove he had an encounter, no one believes his story and instead gives the birthday attention to the dog.
- One of the flashbacks in "Mr. Lisa's Opus" deals with a Forgotten Birthday the year Lisa turned seven, when her first-grade teacher got her hopes up by leading up to announcing a student's birthday only to announce that of her classmate Hubert Wong. She quickly was sent to the principal's office for crying and wasn't even allowed to take one of the cupcakes Hubert had brought to share with the class. The non-flashback portion of the episode (taking place on Lisa's 18th birthday as she writes a college application essay) shows Hubert visiting her house to share a cupcake with her, along with their third Birthday Buddy Luigi, the recurring Italian chef.
- Played With in a Birthday Episode of Teen Titans Go!!, where it's revealed that the years of Starfire's home planet; Tamaran, is twenty times longer than Earth, meaning that Starfire never had any birthdays or any form of yearly celebrations, prompting Beast Boy to share his birthday celebration with her.