It took a lot of work for Sydney Sweeney to get "pregnant."

The Euphoria star, 24, gave her followers a behind-the-scenes look at the long process of creating her pregnant belly for the HBO series. In a series of Instagram Stories, Sweeney summarized how she had a full-body cast made to fit the pregnant prosthetic to her body perfectly.

The first photo showed the completed transformation. "This belly was insane," she wrote on her Story. Then, Sweeney shared videos of herself in a wax and plaster mold, which dried to make a copy of her body.

"Had to do a full body cast so they could make the prosthetic belly," she wrote on a photo. "First layer of goop. Had to be very still," she added alongside a video of someone slathering a blue paste down her arm.

Next came an additional layer. "Then they basically paper macheted me," she said. "Once dried they cut me out of it! It was basically a wax job removing it."

The last photo showed Sweeney putting on the prosthetic belly for filming. "Then they made the belly out of the mold, glue it to me, and paint it!"

The actress also shared a handful of stills from the episode in an Instagram post, writing, "bts and baby bumps."

Sweeney first debuted the prosthetic in Sunday night's episode of Euphoria on HBO. Spoiler: her character, Cassie, isn't actually pregnant (at least, that we know of) in season 2 of the high school drama. The prosthetic was, instead, part of Nate's (Jacob Elordi) daydream during his hospital stay after he was brutally beaten up by Fez at a house party.

In the season premiere, Nate and Cassie secretly hooked up in the bathroom of the party before Fez confronted Nate.

The White Lotus actress spoke about her character's tumultuous relationship with Nate in an interview with Decider. "They've always had a friendship and a little bit of a flirt before we meet them in Season 1, hence why Jacob's character had her nudes," she said. "The attraction was…it's Nate. She knows him. She's also coming from a very low, lonely place. She's drunk and she kind of goes on instincts instead of thoughts."

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