KITKATS may have been around for nearly 100 years, but it turns out many people don't know what's inside the popular chocolate bars.
Fans have been shocked to find out what the secret to the delicious wafer centre is.
You might think it's just a standard crispy biscuit - but there's more to it.
A YouTuber has revealed that crunch actually comes from... other KitKats.
"Some KitKats get broken while they are being made," says the video on Zack D Films channel, which has over two million subscribers .
"And instead of throwing them out the company crushes them up and adds sugar.
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"And that's what's on the inside of a KitKat bar."
KitKat fans were not cool about the revelation
"No way a KitKat is inside of a KitKat I never would have thought," one fan commented.
"That's why it's so sweet!" explained one and "even more delicious" said a second.
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"So you're telling us that we get free KitKats inside of a KitKat?" said another.
Meanwhile some were questioning the chicken and the egg scenario brought about by the revelation.
"I just want to know how they made the first KitKat," pointed out one sharp-eyed commenter.
It's not the first time the secret filling has been revealed though.
An episode of the BBC's Inside the Factory programme in 2018 went behind the scenes of Nestle's KitKat production.
When they drop off the production line, technicians from the quality assurance team remove any KitKats that are deemed to be below par.
This could be because they aren't shiny enough, have too many exterior air bubbles or off-centre wafers, or any other imperfections.
Manufacturers reckon consumers don't want imperfect chocolate bars.
Rather than throwing away the duds, the rejected bars are recycled back into the production process.
They are ground up into a fine paste which goes on to form the filling you find between the wafers.
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Meanwhile people have also been shocked to discover the Cookie Monster's real name.
And Quality Street fans are angry about a change to choc tubs.