Fans go wild as they spot Scarlett Johansson playing the sister in Home Alone as they say: ‘How the heck did I not know this?’

Fans are having a meltdown after realizing that a young Scarlett Johansson will be starring in the iconic festive franchise, Home Alone 3.

The Black Widow actress, 39, plays Alex Pruitt's (Alex D. Linz) sister, Molly, when she was 11 years old.

In the third installment of the festive film series, a young Alex takes on an international terrorist after a microchip hidden in a toy car is accidentally placed in his care.

Sick and at home with chickenpox, Alex sees the unwanted visitors probing the house of his miserable neighbor, Mrs. Hess, trying to find the car and the microchip.

After the thieves realize Alex is spying on them, they decide to set their sights on Pruitt's house – and the Chicago boy is forced to defend the family home.

The Black Widow actress, 39, plays Alex Pruitt's (Alex D. Linz) sister Molly when she was 11 years old (pictured in 2020)

The third part centers on Alex, who is forced to protect his Chicago home from terrorists after a remote-controlled car with a hidden microchip is accidentally placed in his care (pictured clockwise from top left: David Thornton, Alex. D .Linz, Olek Krupa, Rya Kihlstedt, Lenny Von Dohlen)

But fans are also shocked that they didn't recognize Scarlett, who played the main character's indifferent older sister.

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“Holy s***…Scar Jo was in Home Alone?….Wow,” another added: “Scar Jo is in Home Alone 3 and I'm blown away.”

“How did I find out Scar Jo was the sister in Home Alone???”

“Bruh, I never realized Scar Jo was in Home Alone 3,” someone joked.

Others were a little more shocked by the revelation, adding: “Scar Jo is in Home Alone 3 and it blows my mind.”

'HOLY S*** I DIDN'T KNOW SCAR JO WAS THE SISTER ALONE AT HOME 3.'

However, fans weren't the only ones who didn't recognize the Lucy actress; even her own daughter didn't see her in Home Alone 3.

Scarlett is completely unrecognizable in the '90s film and fans seem to agree (Photo: Scarlett and Alex D. Linz)

Fans went crazy after spotting the young Lucy actress in the festive film

During a performance op Late Night with Seth Meyers in 2021, the actress shared that they didn't intentionally show the film to her daughter, but it started naturally.

She said: 'Of course we did Home Alone. And I happened to be in the third Home Alone movie, so I didn't say anything to her because I thought she would make a big deal out of it.”

But the then six-year-old Rosie did not immediately realize that Molly Pruitt was actually her mother, the actress says.

'I really had to, like, [say], “Do you see who that is?” She is [Rosie] like, “Whatever. Is that you?' I thought, 'It's me, your mother.' And she said, “Oh, okay. Whatever”.'

But fans weren't the only ones who didn't immediately recognize the young actress – even her daughter Rosie (then six) took a while to recognize her mother

Macaulay Culkin plays protagonist Kevin McCallister in the original 1990 film