Millie Bobby Brown attends the 35th Annual Paleyfest "Stranger Things" at the Dolby Theatre on Sunday, March 25, 2018, in Los Angeles. Picture: AP

Millie Bobby Brown admitted she and her 'Stranger Things' co-stars used to be "really nice" to one another, but the "honeymoon stage" is now over and they bicker over trivial things.

The 14-year-old actress quickly forged a close relationship with her young co-stars when they began filming the Netflix drama, and though they were initially all "really nice" to one another, they are now like "siblings" and constantly bicker over small things.

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Her co-star Caleb McLaughlin, 16, said: "Once we first met each other I think we were all very outgoing. So it was just easy to connect. It wasn't actually hard."

Millie added: "It was like a relationship actually because it felt like we went through a honeymoon stage.

"We would be, like, really nice to each other. We didn't want to do anything that would hurt each other's feelings.

"Now it's so different. We are actually siblings. We argue all the time."

But Millie admitted the arguments are over trivial matters such as "Why are you eating my chips?"

Caleb added: "It's little remote control arguments."

But one person who stays out of the squabbles is Sadie Sink, who only joined the cast for the second season.

Speaking during a panel chat at PaleyFest on Sunday, Millie admitted: "Sadie doesn't argue though! She's like, 'Guys, everybody calm down.'"

The cast will be returning to work in the next few weeks but stayed tight-lipped on what will happen in the next season of the supernatural drama.

Director Shawn Levy said: "I'll get in so much trouble. I can't say much. But we are going back to work next month and we're super excited."

Millie shaved her head for her role as Eleven on the show and she recently admitted it was the most "empowering" thing she'd ever done.

She said: "The day I shaved my head was the most empowering moment of my whole life. The last strand of hair cut off was the moment my whole face was on show and I couldn't hide behind my hair like I used to. As I looked in the mirror I realised I had one job to do. Inspire ... Shaving your head is so empowering. You don't need hair to be beautiful. You are beautiful with or without. I learnt that too x (sic)"