Do you know any stories where a changeling forgets it's a changeling and thinks it is the pony who it's impersonating?

Ideally, one where Chrysalis herself is convinced she's Cadence.

Maybe the reverse too. One where Cadence is worried that she might be Chrysalis.

Closest I can think of is Solitary Locust. Which never completed, but it satisfies your conditions, just not Cadance.

BTW, I would totally read a story where Chrysalis convinces herself she's Cadance. Since it's close to the conceit that Chrysalis is Cadance's Nightmare form, like Daybreaker or Nightmare Moon.

6460035 Is it wrong of me to think of it, like, Chrysalis just walks into their home one day and goes "Honey, I'm home!" and kisses Shining in front of Cadence, Flurry, and Sunburst?

The Love Bug is the first one I thought of, with amnesiac Chrysalis. Not impersonating anyone, but has her own identity.

there is a story where Chrysalis has been Cadence since she suffered a fatal accident long before Shining met her

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She'd be double blasted before she got close enough to kiss.

6460075 That or too stunned by her being legitimately sweet, probably.

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Just finished 'Love Bug.' I liked that one.

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Link it?

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There's quite a few where it's one or more of the Mane Six that're changelings without their knowledge but I can think of none where it's Cadance. Not sure if there's been one where Cadance takes over the hive from Chrysalis however. Been a few where Chrysalis passes the crown to Twilight, either by choice or force, revealing the girl's true heritage. (Though most hive-takeover fics would result in the pony transforming into a changeling Queen if they weren't already) [DarthVader_I_am_your_father_Luke_nooo.gif]

And there's that series where it's Celestia, in the far past, leaves her throne to an imposter "because reasons" and no one up until now realizes their loving princess is a changeling queen-- who might as well be Celestia since many generations grew up under her rule and know no different.

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https://www.fimfiction.net/story/62301/true-love-never-changes

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The Monster In The Twilight, wherein Cadance inherits the remnants of the hive after Twilight obliterates it with a clever but horrifying spell.

Damaged likes to engineer situations in which Cadance and Shining Armor end up taking the hive away from Chrysalis due to bugification shenanigans.

How about https://www.fimfiction.net/story/86542/winds-of-change ?

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Doesn't even mentioning the title take away some of the suprise if it's a plot point?

Anyway, I do know of one such fic.

There is one story I've read where a changeling forgets he's a changeling. Goldfur's story Conversations in a Canterlot Cafe has this as a minor plot point in one chapter.
Raugos's story That Changeling's a Pony does something of the reverse.

Hi.
I've seen a few that more or less fit your criteria:

https://www.fimfiction.net/story/146384/broken-little-changeling
This is a story centred around Cadance's mother, who happened to be a changeling.

https://www.fimfiction.net/story/199770/deep-cover-confusion
This story is a humorous twist on your premise: every single pony in Equestria happens to secretly be a changeling, and every single one of them thinks they (and their direct family) are the only changelings around.

https://www.fimfiction.net/story/72594/the-alicorn-delusion
All Alicorns are, and have always been, changeling queens.

https://www.fimfiction.net/story/284555/change
Twilight didn't know it, but she was always a changeling. And the whole royal wedding thing wasn't an invasion, but a retrieval mission. A very good story, this one.

https://www.fimfiction.net/story/26961/mirrors-image
The same premise as the previous one.

https://www.fimfiction.net/story/295234/a-changing-perspective-or-how-i-learned-to-stop-worrying-and-love-the-shell
Peace has been achieved between ponies and changelings, but not acceptance. Chrysalis happens to hear Diamond Tiara say a racist remark -regarding changelings, and then turns her into a changeling and deposits changeling-Diamond back into her own life, terrified to be uncovered.

https://www.fimfiction.net/story/37342/quorum-sensing
Scootaloo didn't know that she happened to be a changeling...

https://www.fimfiction.net/story/130066/a-filly-called-pet
This one is a bit disquieting: a pony filly is raised in Chrysalis' personal chambers, and thinks that she just happens to be a changeling that doesn't change. Meanwhile, her real function is being Chrysalis' personal snack.

https://www.fimfiction.net/story/131032/two-minds
Well after the wedding invasion... Cadance, Princess regnal of the Crystal Empire, is dying of a curse lain on the throne by Sombra. She secretly enlists Chrysalis to replace her on the throne, but twists the deal by uploading her own mind into Chrysalis. Chrysalis is thus semi-possessed.

https://www.fimfiction.net/story/206365/chitin
Don't actually remember how this story goes, but Twilight casts a massive changeling revealing spell, and turns out that 20% of Ponyville were actually changelings.

https://www.fimfiction.net/story/108555/x-is-a-changeling
A random comedy: Every animal in Fluttershy's cottage happens to be a changeling. And they call her queen despite her actually being a pony.

https://www.fimfiction.net/story/83190/changeling-blood
Backstory to this story: the young changeling prince is an orphan because his Mum was sent on a deep cover assignment and "went native" (forgot her real self and became the character).

https://www.fimfiction.net/story/199269/lyra-visits-bon-bon-in-jail
Bon Bon happens to be a pony who thinks she's a changeling stuck in disguise...

https://www.fimfiction.net/story/25148/all-american-girl
This story is a fully blown technothriller, but among its many interconnecting plots, we include that a changeling princess becomes convinced that Chrysalis is not her real mother, and thus has to go to her mother, Twilight Sparkle. (She does know that Chrysalis is her biological mother, but then becomes a thing about "blood thicker than water" and becomes obsessed that Twilight will adopt her.)

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https://www.fimfiction.net/story/241283/deep-cover
This story here may fit your criteria.
The actress who plays Applejack is such a perfect method actress that she never, ever breaks character. Or is it that she has come to think that she is Applejack? Is she even a pony at all?

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Wow! You sure know your changeling stories.