Prince Harry and Meghan Markle had a secret animal-onesie-themed engagement party and wore matching penguin outfits

• Volume I of "Harry & Meghan" dropped on Netflix on Thursday.
• Episode two revealed Prince Harry and Meghan Markle had an animal-onesie-themed engagement party.

Meghan Markle and Prince Harry had a secret engagement party before the world knew they were getting married, and it had a playful twist.

On Thursday, Netflix released Volume I of "Harry & Meghan," the docuseries about Harry and Meghan's relationship and experience as senior royals.

The first three episodes included many details about their romance previously not shared with the public, including the fact that they met on Instagram, and in episode two, the pair and their friends opened up about their 2017 engagement, sharing new details about their proposal and intimate engagement party.

"They were gonna keep [their engagement] quiet because it was gonna be announced a few weeks later," the couple's friend Lucy Fraser said, speaking of the formal announcement that was made on November 27, 2017. "We had a little engagement party, and everyone was dressed in animal onesies."

The docuseries didn't include any photos from the engagement party, but Fraser said Harry and Meghan dressed as penguins for the event.

"Meg and Harry were dressed in matching penguin onesies, because penguins mate for life," she said. "And they were so sweet. And we had so much fun."

The docuseries also shared new details about their engagement. The Sussexes previously said in a BBC interview they got engaged while they were roasting a chicken at home, but the moment was more involved, as they shared in the episode.

"I wanted to do it earlier, but because I had to ask permission from my grandmother, I couldn't do it outside of the UK," Harry said of proposing to Meghan. But by November 2017, they were living together on the grounds of Kensington Palace in the UK, so Harry could pop the question.

He said in episode two that he set up a romantic proposal spot in "the north garden being overlooked by the staff flats." He tried to make it a surprise, but Meghan had an inkling it was coming, they shared.

"I did pop a bottle of champagne while she was roasting a chicken, and that kind of slightly gave the game away," Harry said.

A photo of the proposal shows a picnic blanket surrounded by electric candles and roses, and the couple's dog, Guy, was there as well. Harry confirmed he got down on one knee to propose.

"I was so joyful and excited," Meghan said of how she felt after they got engaged.

Volume I of "Harry & Meghan" is available on Netflix. Volume II will air on December 15.