'The Walking Dead' hired 5 sets of twins to play zombies in those mysterious visions on Sunday's episode

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Carol was actually seeing double on Sunday night's episode of "The Walking Dead."

Warning: There are spoilers ahead for Sunday's "The Walking Dead."

"The Walking Dead" introduced a lot of new characters in Sunday's episode - including a tiger! But you may not have noticed the five sets of twins who were brought in to create one of the night's most bizarre moments.

Carol's mysterious visions at the start of the episode weren't explored much in Sunday's episode, but in the visions, Carol starts seeing what the zombies looked like while they were still human and before they were dead.

In a behind-the-scenes video on the making of the episode, executive producer Greg Nicotero explained Carol was flashing between the living world and the dead. While we don't learn more about those odd flashes for now, the "Talking Dead" aftershow said the series had five sets of twins on the show to bring Carol's surreal visions to life.

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"My immediate response to that was, 'Well, we should hire twins,'" said Nicotero. "From a production standpoint, we would film the twin in the clean wardrobe and then we'd bring the walker version in in the aged wardrobe and the zombie makeup and composite them in."

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First they would film the twin in the cleaned up outfit.

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Afterwards, the zombified twin would come out.

VFX supervisor Victor Scalise said one of the challenges of filming the scenes twice was making sure that the lighting and the positions were exactly the same. Slight differences would determine how jarring the scene could wind up.

Here are a few of them from Sunday night's episode:

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You can check out the feature below which also shows how the series' new tiger was brought to life: