Here's everything you need to know about Young Sheldon.

Young Sheldon is The Big Bang Theory spin-off no one really asked for.

It’s also been an instant hit.

The sitcom premiered in Australia on Monday night and absolutely smashed the ratings – beating out the long-awaited reality TV show/revolving sex door that is Bachelor in Paradise.

A whopping 1.053 million viewers tuned in for the Australian premiere, and the show attracts an average of 15 million viewers per an episode in the US.

Young Sheldon is kind of like a prequel to the popular long-running sitcom. It follows the story of Big Bang fan favourite, Sheldon Cooper, as he grows up in a small town in rural Texas.

The sitcom is a little bit Malcolm in the Middle and a little bit Roseanne, with a good sprinkling of that Big Bang comedy fans have grown to love.

See how Sheldon became Sheldon in this The Big Bang Theory spin-off. Post continues.

So what makes this sitcom so goddamn popular?

Simply put – it’s the Sheldon factor.

People love Sheldon and they can’t get enough of him.

The younger version of the iconic character is portrayed by Big Little Lies’ Iain Armitage in the series.

Armitage scored the role after two casting agents sent creator Chuck Lorre his audition tape, which was recorded at his grandmother’s house. Lorre immediately knew he was perfect for the role. He’s basically a mini version of Jim Parsons who plays the character in Big Bang.

“We looked at it and went, ‘Oh my god, we can’t possibly be this lucky,” Lorre told Channel 4. “He was just spectacular.”

Young Sheldon is narrated by Parsons, who is also an executive producer on the show.

A Big Bang Theory die-hard breaks down the appeal of the show. Post continues. 

Parson’s told CBS, he’s struggled a little bit with making the transition to a behind-the-camera role.

“It’s very strange and it’s taken a lot to get used to, even talking to another actor, in this case, Iain,” Parsons said.

“I’ve never been someone comfortable giving another actor direction. I don’t know what makes any other actor tick, necessarily, and I don’t want to break it, or him!”

Armitage, who was also at the interview, replied: “I’m not that fragile”.

“I’m fragile, but not that fragile.”

The series begins in 1989 when Sheldon is nine years old and about to start high school along with his older brother.

The show will follow Sheldon as he makes his way through high school and struggles to be understood by his classmates, teachers and siblings.

It’s bound to be full of laughs and classic Sheldon one-liners.

You can catch up on the first two episodes of Young Sheldon on 9Now.

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