The unlikely story behind why Meryl Streep joined Big Little Lies.

In case the female-led Big Little Lies cast including Reese Witherspoon, Nicole Kidman and Laura Dern wasn’t already fist-pumping enough, another big name has been announced for season two.

Meryl bloody Streep.

As an advocate for women in Hollywood, Streep is a natural fit for the groundbreaking (and award-winning) drama series adapted from the bestselling novel.

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But author Liane Moriarty dropped a major bombshell after the announcement.

Turns out there was a not-so-hidden clue that she always wanted Streep in the role. In fact, the part was practically written for her.

Streep will play Mary Louise Wright, the mother of Perry Wright, played by Alexander Skarsgard.

"When I was writing the [season two] story, I actually called her Meryl to myself because I was thinking who would be more perfect than Meryl to play Perry's mother?" Moriarty told Fairfax Media yesterday.

Listen to Mia Freedman, Laura Brodnik and Jackie Lunn talk all things Big Little Lies, on our pop culture podcast. WARNING: Spoilers ahead. (Post continues...)

"Not only is she an incredible actor, but they're quite similar in appearance. But that was my own, secret game."

The author also said she looked up Streep's middle name to discover her real name was Mary Louise. And so the character got her name.

"I said to the producers – not quite believing my own audacity – I have this role and I think Meryl will be really perfect for it," she said.

Big Little Lies season two will air on HBO in 2019.