Jack Black is having "nightmares" ahead of his return to 'Saturday Night Live'.

The 'Minecraft Movie' star last hosted the comedy sketch show almost 20 years ago and he admitted it feels "cray cray" to be returning to the programme after so long, but he's also looking forward to his guest stint on 5 April.

Asked how he is preparing for the show, Jack told Variety: "Just you know, having lots of nightmares and night terrors and also fond memories flooding back. It's crazy, very exciting."

The 55-year-old star - who also guest hosted 'SNL' in 2002 and 2003 - admitted he doesn't yet know what sketches he will be involved in and thinks that's what makes the role so exciting.

He said: "You know what they're thinking about right now? They are just all in a dead coma from last night's show.

"Maybe some of them are thinking of some ideas, but I'm really thinking it's one of those shows they put together in one week, that's part of the excitement."

Jack loves "all those kids" from the current 'Saturday Night Live' cast.

He added: "I call them kids because I was on that show before some of them were born -- except for Kenan [Thompson], we're around the same age. That's about it."

Meanwhile, Jack admitted he was aware of the "Minecraft universe" before taking on his latest role as expert crafter Steve in 'A Minecraft Movie'.

He said: "I did do some Minecraft gaming, yes! I wouldn't call myself an expert, but yeah, I know my way around a Minecraft universe," he said.

The Tenacious D rocker performs 'I Feel Alive' - which features Dave Grohl on drums - in the film and admitted he was delighted when Mark Ronson and Andrew Wyatt were brought in to write the closing number for him.

He said: "I'm very excited about that one.

"Cale [Boyter], our producer, was like, 'We need a big song at the end, something that wraps up the whole movie.' And I was like, 'I can't write a song that wraps up the whole movie.'

"I said, 'Maybe if you could get those guys that wrote "I'm Just Ken," they could do it. And he said, 'Done!' and made it happen.

"I was like, 'Are you kidding me?' And we started jamming and working together and I was like, 'Oh my God, this is heaven.'"