Characters often recall things when it would be just too late to actually use that information.
It could be an important code to use on a spy mission, or what not to say to a king when on a diplomatic mission, or what a guy is allergic to when making him dinner.
And those things can all be either Played for Laughs or Played for Drama. Also, the audience might be let in on this bit of information, or we might not. The former helps create suspense, while the latter comes as a form of The Reveal.
This can overlap with Now You Tell Me if someone forgot information they need to tell someone else. Can also overlap with Explain, Explain... Oh, Crap! if one remembers the implications while talking.
This kind of thing isn't that implausible in Real Life, as anyone who tried to recall memories or information, and couldn't remember it until minutes or hours later, can attest.
A Sub-Trope of Irony. A Super Trope to Forgot I Couldn't Swim. Compare Spanner in the Works, Something We Forgot, You Are Too Late, Repressed Memories, and Remembered I Could Fly. Contrast Just in Time and Photographic Memory.
This trope is about forgetting something, not being given information one didn't know before.
- According to the first Magical Girl Lyrical Nanoha Compilation Movie, this is the Tragic Flaw of the Big Bad Evil Matriarch Precia Testarossa (this bit of her characterization differs from the original anime, where she was just a total monster). As she plummets to her death, she suddenly remembers that her beloved late daughter Alicia, who she had done many of her more evil things to bring back, wished for a little sister — in other words, she wished for Fate, whom Precia treated like crap and rejected earlier for not being exactly like Alicia. She then muses to herself on how she never notices things until it is too late.
- In the first season of Higurashi no Naku Koro ni, Shion, in full psychotic Yandere mode, realizes that she forgot the last request of her beloved Satoshi, which was "I leave Satoko in your care." She realizes this just as she's finished tearing the poor girl apart with a knife. No, it is NOT pretty.
- Played for Laughs in the third episode of Servant × Service, where Hasebe trying to, but keeps on forgetting to ask Yamagami for her email address — he gave several favours to Yamagami which would be opportunities to do that, but he only remembered that after Yamagami left.
- One Piece:
- Played for laughs in the Alabasta arc, where Vivi often forgets to tell her friends about the dangers of traversing the deserts until said problem has already appeared or been taken care of.
- Played for drama in the Dressrosa arc, when the reader learns that the reason Ace and Luffy's brother Sabo never tried to contact anyone from his past who thought he was dead was because he suffered Laser-Guided Amnesia. The restoration of his memory isn't triggered until more than ten years after its loss when he learned about the events of the Paramount War, where Ace was killed. The discovery sends the poor guy into a screaming, crying meltdown.
- Mekakucity Actors: Episode 11 opens with the Shintaro of another timeline, apparently still a shut-in, unlocking his power and remembering the events of past timelines. When he realises that the same thing will inevitably happen again (if it hasn't already), he decides to kill himself now, and hope the next him will remember before it's too late.
- A few gags on Millie the Model involve this. One was her getting ready to model for a huge cigarette campaign, and then remembers that she doesn't smoke.
- The second arms dealer in Diamonds Cut forgets to turn up to the final meeting. Apparently, he only survives because of that.
- Chit Sang in The Stalking Zuko Series forgot to tell Zuko about cooler fever until he'd already got extremely sick to Katara's annoyance.
- From Gensokyo 20XXV, we have a rather heartbreaking scenario with Renko, who, due to illness, suffers from a degree of blindness and memory loss, so she didn't remember that Ren, the "puppy", had passed away, and neither did she remember him too much before his passing, due to said memory loss. When she does remember, she scrambles about the apartment building trying to find him and asks about where he is and when he'll come back, Reimu had to sit her down and explain, as only she could, that he's passed on. Wren is justifiably upset.
- In Under the Dome by Stephen King: As police chief Randolph and a detachment of officers are heading towards a meth lab in order to assault it and take the valuable propane stored there, Randolph realizes that they had forgot to grab body armor (i.e. bullet proof vests) before driving to the lab. He doesn't worry too much about it, since he figures the assault will be easy; he assumes the two men there will be too stoned out of their minds to fight back. How wrong he turns out to be.
- In The Princess Bride Miracle Max promised that the miracle pill he made for Westley would last for a full hour. It's only after our heroes have left that he realizes that he messed up the proportions of ingredients and if it lasts for forty minutes it'll be a miracle. This is what causes Westley to collapse during the confrontation with Humperdinck. This was altered in the movie because to do it the grandfather would have to give timestamps.
- Early in Harry Potter and the Order of the Phoenix, Sirius gives Harry a Christmas gift, telling him it can be used to contact him in an emergency (or if Snape gives him a hard time in Occlumency lessons). Harry, knowing Sirius is going stir-crazy and not wanting him to charge off, hides it away. He then forgets about it until well after misinformation from Voldemort gets Sirius killed, something which could have been easily prevented with the use of that gift.
- In Anne of Green Gables, Anne serves Diana what she thinks is Raspberry Cordial (at least that's what Marilla told her was in the pantry). After Anne's barred from seeing Diana again after getting her best friend Unsuspectingly Soused, Marilla storms to the pantry, grabs the bottle—and discovers it's currant wine, and the cordial is in the cellar. Anne herself never drank any of it, so she couldn't tell.
- Our Miss Brooks: In "Wishing Well Dance", Miss Brooks get in trouble with Mr. Conklin after Stretch Snodgrass gives her a message to see him immediately. The problem? Stretch Snodgrass forgot about the message, only remembering to give her the message hours later.
- In a season 4 episode, when Radar acquires a glass of tomato juice, Col. Potter remembers it fondly as it is a rare treat from home in this hellish war zone. Radar kindly gives the Colonel the glass and the Colonel enjoys it. So, Radar sets upon a chain of deals to get more for the Colonel. However, at the end of the episode, the Colonel won't touch another glass. In his enthusiasm to have something nice, he forgot he was mildly allergic to the stuff and suffered heavy congestion and discomforts the night after his previous glass.
- An episode of has Charles using this as a ploy to yank Col. Flagg's chain. Hawkeye is accused to be a traitor by an infirmed colonel for giving priority to a wounded North Korean soldier. Col. Flagg arrives and retrieves a notice which Charles happens to notice first. The notice tells of a meeting in the Swamp with Hawkeye, Col. Potter and two Korean officials. Col. Flagg bursts through the meeting, thinking a plan is afoot for North Korea to overtake South Korea and that Hawkeye and Potter are in cahoots ("Caramba! The fish stinks from the head down!"). It turns out to be a poker game, and the two Koreans happen to be the Mayor and Chief of Police of Panmunjam. Charles conveniently now recalls who the two Koreans are and embarrasses Flagg.
- The guys from Top Gear once took on their German counterparts in a series of challenges. One of these was a six-way drag race with the Brits in cars manufactured by former World War II Allied nations and the Germans in cars manufactured by former World War II Axis nations. But while the Germans were all able to attain performance cars from Germany, Italy, and Japan, the British were only able to get British and American cars because they couldn't think of a third Allied nation that makes good performance cars. Finally, James pulls up to the start in an Indian G-WIZ, a car often derided on the show due to its poor performance and perceived lack of build quality, and resigns himself to using it. Just as the race is about to start:
James: Cock, I just remembered the Australians. They do that VXR thing.
- When Lois is in the final days of her fifth pregnancy in Malcolm in the Middle she announces with Hal their doctor has decided to induce labor on a certain day. Dewey is horrified when he learns which day in particular, because it's his birthday. When Hal takes the boys to a bridal expo (having thought they were attending a car show), Dewey slips away and starts introducing himself to several members of the expo staff and those who have booths, telling each of them "A story." It culminates in the staff and professionals helping stage a massive guilt trip on Hal, where Dewey tells his life story over the convention center's intercom before asking if Hal remembers anything special about the day they're inducing labor. Hal gets fed up before demanding to know what the big deal is when Dewey reminds him it's his birthday, eliciting vocal disgust and outrage from the people at the expo. Hal claims it's not Dewey's birthday before he does some thinking and realizes it is.
- In A Funny Thing Happened on the Way to the Forum, Pseudolus is trying to read a recipe for a potion, and then remembers that he can't read. Fortunately Hero is right there to do it.
- Dm C Devil May Cry has this little gem during the raid on Mundus' HQ:
Dante: So, I think she said 105th floor yeah, that's it.
Kat (flash back): Go to the 106th floor. No matter what, don't stop on the 105th, it's filled with enemies.
- In Fire Emblem Awakening, Emmeryn loses most of her ability to speak and forgets almost everything of her life as Exalt due to suffering brain damage after her attempted Heroic Suicide. If she dies in Classic Mode, these are her Famous Last Words.
"I...I finally remember...But alas...I am too late... Lissa...Chrom...forgive me..."
- Persona 3: In a much more tragic twist on this trope, the protagonist begins dying, and holding on by sheer willpower alone. He holds on for two entire months, just to fulfill a promise to his friends that they would meet on the rooftop on the day of their graduation, so they can look back on the world they saved. However, after the battle with the final boss, and he seals it away, the protagonist's teammates and closest friends forget the previous year they spent together, saving the entire world. In the final moments, the protagonist waits on the roof with Aigis, probably sad that they couldn't be there, and barely hanging on to life. His friends suddenly remember their promise, and rush to the roof to meet him. However, the protagonist slips away only seconds before they reach the rooftop.
- In Sonic Adventure 2, Shadow's driving motivation is his promise to avenge the death of his friend Maria by destroying humanity. When the ARK's been activated and is on a collision course for the planet, Amy tries to convince Shadow to help them stop it. It's then that Shadow remembers that what Maria had actually asked of him was to do what he could to make the people of the world happy. Kind of an important distinction there, Shad.
- It is justified since Shadow's creator implanted him with False Memories. What happened in that case is less "forgot until now" and more "was overwritten by something else until now".
- After Ultima IV Smith the horse became a running gag for this for the rest of the series. Due to a bug, he failed to deliver a critical clue in IV, and every later appearance he would remember something important he had to tell the Avatar: information that would've shortened the previous game had he relayed it then.
- In The Order of the Stick Roy asked an oracle a question, and then realizes his question was poorly worded based on extraneous interactions with the Oracle, and worse, he immediately forgets even that the question was poorly worded, due to a memory spell in the oracle's home which erases all memories about the visit except one's question and the answer (including knowledge about the memory spell).
- Which leads to some Fridge Logic about why he kept walking out of the valley instead of turning around immediately (since he hadn't had his memory affected yet since learning about the memory spell).
- In Gunnerkrigg Court, Annie's order for Reynardine to shut up is treated as Something We Forgot, but it also stopped Rey from telling her about the possessed Robot.
- In the El Goonish Shive arc "So a Date at the Mall," Tara the griffin is manipulated into attacking Elliot by an Immortal because she mistakenly believes that Immortals are incapable of lying. The catch is that she should have already known that this is incorrect. Her wife Andrea previously informed her that one of the differences between their world and the main world is that Immortals in the main world can lie all they want. Unfortunately, she was too distracted to maintain this information, and was only reminded long after it ceased to be relevant.
- In Cucumber Quest, Princess Nautilus spent much of her youth studying the myths and stories about the Nightmare Knight and his underlings, and is excited to play the role of Cucumber's Mr. Exposition... but also has an unfortunate tendency to forget crucial details "until the exact moment it stops being helpful". This is best demonstrated when she forgets that Noisemaster and Mutemaster come as a Dual Boss, and later on when she admits that, had she remembered what Rosemaster's powers were in advance, it would've saved them a lot of grief.
- In Adventures of the Gummi Bears, Cavin takes some Gummi Berry Juice to fight some trolls, and when nothing happens, Zummi just remembers that the juice only works for humans once a day.
- Toy Story: "Wait a minute... I just lit a rocket... ROCKETS EXPLODE!"
- Displayed directly in the final episode of Futurama when Fry intentionally drops from the roof of a building in response to Leela's supposed rejection of his marriage proposal; however, as he falls, he notices Leela entering the building to meet him. Fry laments over this for a few moments before remembering that he has a button that allows him to travel backwards in time by 10 seconds. Unfortunately, the time that Fry spent lamenting his decision after noticing Leela extended his fall past 10 seconds and the button allows him only to loop a sequence of falling, as the button requires 10 seconds to recharge.
- In The Grim Adventures of Billy & Mandy Christmas Special, Mrs. Claus sends Grim, Mandy and a vampire into the lair of a vampirized Santa Claus. This exchange follows.
Baron Ghoulash: I just remembered. Mrs. Claus is the Head Vampire!Mandy: That information would have been useful five seconds ago!
- Dastardly and Muttley in Their Flying Machines: "Stop Which Pigeon" has Dastardly agreeing to participate in a scheme to catch the pigeon by diving off a diving board attached to one of the planes and into a swimming pool connected to another plane. But Dastardly seems to be forgetting something. The plan works beautifully, but Dastardly releases the pigeon when he now remembers:
Dastardly: I CAN'T SWIM!!
- Freakazoid!: Freakazoid is being chased in his Freakmobile by the villain, Longhorn in semi-truck. As both vehicles near the ocean, Freakazoid decides to see if Longhorn's truck comes with underwater options. As it turns out, Longhorn's truck does, but the Freakmobile doesn't and ends up crashing into the ocean floor and flooding.
Freakazoid: Oh that's right. This car was never designed to operate under water. Wow! That was important, and I forgot it!