Deceptive Legacy

Often a couple will bear a child and then split up under acrimonious circumstances. Although this is the case and the mother and father bear ill will toward each other, the remaining parent (or other parental figure) doesn't want to poison the child's mind against the other parent. Or they really would prefer not to have to admit to the child or anyone else that they were abandoned/left.

Or one person will abandon the relationship leaving the other hurt. But still, a child is an innocent.

Or the missing parent is in some sort of special circumstnace, regardless of feelings on either side.

So they'll tell a comforting lie or spin an embellishment of the truth that will allow the child to grow up proud of (or at the least, not ashamed of and humiliated by) their Disappeared Dad or Missing Mom. If the vitriol is sufficient, the reverse will also be true. The lie told about the parent is to make the child ashamed, and the truth is they are a better person than the child was led to believe.

Sometimes the child grows up and finds out the truth and is disappointed. Sometimes the child grows up to find out the truth and doesn't care because they're simply happy to have the other parent in their lives again. The parent can also not care they've disappointed their progeny, or they can live up (or down) to the expectation placed on them by what the child was told.

Occasionally it's a mentor figure who does the deceiving about the legacy of their absent parent. Guilt over keeping the truth from the innocent child may result in a Revealing Hug.

Usually this is a Disappeared Dad being lionized or demonized, but occasionally it's the Missing Mom.

Contrast Tell Me About My Father. I Wished You Were Dead is related in a roundabout way, but in this trope, it's usually one parent or the other declaring that the other is "dead to me". Also related to Motivational Lie, as a child burdened with shame might need the lie to go forward, or a child burdened with shame may get angry enough to overcome what s/he believes is their parents' awful legacy.

Anime and Manga

 * In the Speed Racer episode "Man on the Lam", an escaped convict comes across a house in the woods where a little a blind girl lives all alone. He enthusiastically greets and hugs her, commenting on how big and heavy she had gotten. She tells him that her father had died and her mother was off making money for surgery so she could see again. The man tells her that he was an old friend of her father. It is later reviled that she is friends with Sprital. Leading and after the storm he takes Speed hostage and makes him drive to where the loot was stashed. This leads to a mountain chase and shootout with the police and other criminals involved in the robbery ending with the man getting the mortally injured and telling speed to give his eyes to the little girl who was his daughter.

Comic Books

 * Marvel Comics:
 * X-Factor: Hangman's ex, the mother of his son, lied and told the boy, Terry, that his dad is a super hero when the opposite is true. Hangman is astonished to hear this, but goes back and tries to do something heroic for the sake of making his son proud.
 * Daredevil: Played with. The Kingpin killed Echo's father, but honored the man's Dying Wish to raise her like his own. So Fisk told Echo Daredevil killed her father. She eventually found out the truth. It was not pretty.

Film

 * Armageddon: Chick's wife, ashamed of his gambling problem, and angry that he showed up unnanounced to see his son before going into space tells their small son that Chick was "a salesman". She changes her story, though, when the news reveals that Chick is on the teams going to save Earth from a giant asteroid.
 * The eponymous character of Forrest Gump has a Disappeared Dad and his mom tells people that "he's on vacation." Though Forrest tells us that she told him that "he's on vacation" means he's never coming back, we don't see her clarify this for other people.
 * In O Brother, Where Art Thou?, Everett's wife Penny tells their daughters that their father died, rather than tell them he's in jail.
 * In Star Wars: A New Hope, Obi-Wan tells Luke that Darth Vader killed his father. We know that Vader reveals that to be a lie (after a fashion: Obi-Wan considered Anakin dead, and grieved his loss, once he went over to the Dark Side and became Vader).
 * In The Mask of Zorro, Elena was raised to believe Don Rafael was her father. But Rafael ordered the attack on Don Diego de la Vega which resulted in Esperanza's death. Rafael took Elena as his own because he'd loved Esperanza, but she'd chosen Diego. Elena grew up believing her mother died in childbirth. When Diego returns, he sets the record straight.

Literature

 * In the Harry Potter books, the Dursleys, Harry's abusive and mundane aunt and uncle, make out his parents like terrible people. Harry only finds out they're revered with love once he meets the Wizarding community.
 * In the first book of the Percy Jackson series, it's admitted near the beginning that the eponymous character's mom claimed his father was lost at sea. Of course, the truth eventually comes out.
 * In the Warrior Cats graphic novel trilogy Tigerstar and Sasha, Sasha gets pregnant with Tigerstar's kits before she realizes that he's a power-crazy murderer bent on ruling the entire forest. She raises her kits on her own, only telling them stories about how their father Tigerstar was strong and brave and that he'd be proud of them. A while after Tigerstar's death, Sasha takes the kits to RiverClan. Imagine the kits' shock when they see young RiverClan cats pretending to be the evil Tigerstar and reenacting his death.

Live Action TV

 * In the Doctor Who episode "Father's Day", Rose's mother Jackie tells her that her dead father Pete was a great inventor and entrepeneur. Then Rose goes back in time & meets Pete, and discovers he's a bit of a prat.
 * In Friends, Phoebe's grandmother (on Phoebe's mother's instructions, it turns out) tells Phoebe that her father is a tree surgeon worshiped by villagers in South America. She also buys photo frames and tells Phoebe that the stock photo of the guy who comes with the frame is her father. This was done so Phoebe would feel like she had an interesting dad, but would never try to track him down.
 * Glee: It turns out that 's mother had been lying about her husband the entire time -
 * How I Met Your Mother, Barney's mother told him that his father was Bob Barker (because he was who happened to be on TV at the time). Barney clings to it because he wants an awesome dad. This was to cover up the identity of his real father, who Barney's mother didn't want in the picture.
 * Once Upon a Time: Emma tells Henry that his biological father was a fireman and a real hero, who died heroically. She has nothing to remember him by to pass on to Henry, and whether this turns out to be false remains to be seen.
 * In Raising Hope, Jimmy's mother Virginia was raised by her grandmother (Maw Maw). Maw Maw claimed that Virginia's mother had died when trying to get honey from bees - she apparently put a plastic bag over her head to protect herself from the bees, passed out, fell, and hit her head on a porcelain duck. It turns out that Maw Maw was just lying to protect Virginia from the fact that her mother abandoned her.
 * In Veronica Mars, one of the cases of the week the eponymous character receives is to track down a classmate's father. It turns out that his mother told him that his father was dead to hide the fact that his father has had a sex change.

Western Animation

 * In Futurama Leela's parents left a note written in an alien language after dropping her off at an Orphanerium (which served as a Rosetta stone for fans since the same language appeared elsewhere in the show and a translation of the note was given) so she (and everyone else) would think that she was a Human Alien rather than . This is an odd case of both parents being missing and telling the lie in the hopes of improving the life of the child.
 * G.I. Joe: Renegades: Storm Shadow tells Jinx that Snake Eyes killed her father. The odd truth is that Storm Shadow believes it to be true, but it is not. But he convinces Jinx to renounce her connection to Snake Eyes and take up her name as Kim Ashikage.