Jack Black shared a bit more than he was planning during his appearance on a late night talk show on Monday. 

And it was not a gag. 

The actor, 55, thrilled the audience at The Tonight Show starring Jimmy Fallon when he pretended to shred a guitar while walking through the crowd to promote the upcoming A Minecraft Movie. That is when he suffered a wardrobe malfunction. 

As Black approached the stage, his black pants began to slowly but surely slide off his hips, revealing a black-and-red boxer brief, which clashed with his green print shirt. 

After being greeted by Fallon, 50, with a hug, the Kung Fu Panda star quickly pulled his pants up, but pushed away any embarrᴀssment by swiveling his hips and waving to the cheering crowd. 

‘That is Jack Black. That’s how you make an entrance!’ Fallon exclaimed. ‘You bring the heat. You bring the energy,’ he continued.

‘I didn’t bring a belt,’ Black quickly quipped. 

Jack Black, 55, revealed a little more than he intended when his pants fell down as he stepped on the stage for an appearance on The Tonight Show Starring Jimmy Fallon Monday night 

While talking about the Golden Globe nominee’s latest project, which is based on a popular video game, Fallon took a walk down memory lane saying ‘I think your career started as a video game commercial.’ 

‘My first job was for a game called Pitfall on Atari,’ Black affirmed, reminding the audience it was ‘the very first video game’ for the Atari home system, as way of introduction for a brief look at the spot.

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The Tenacious D frontman revealed he also used his musical talents in the film. 

‘I’ve got some little nuggets, a sprinkling of musical nuggets and a big showstopper,’ he said.

‘They wanted a song at the end of the movie that wraps up the whole… and they got the guys that wrote I’m Just Ken from Barbie, and I was like Mark Ronson and Andrew Wyatt? And so we jammed on it and wrote it together and it’s really…’

‘It’s so good!’ Fallon said finishing his friend’s sentence. 

The versatile star revealed it was his sons, Sammy, 18, and Tommy, 16, who introduced him to the video game. 

 ‘They were on to Minecraft 10 year ago, way before the movie was even talked about. And I learned how to play Minecraft just because I wanted to be able to speak-a their language’ he said with a fake Italian accent. 

‘I didn’t bring a belt,’ Black quipped, brushing away any embarrᴀssment by swiveling his hips and waving to the cheering crowd

The actor was promoting A Minecraft Movie, with Jason Momoa and Sebastian Hansen, which opens Friday 

The actor and musician  thrilled the audience while ‘shredding’ a guitar for his intro

The  Tenacious D frontman shared that he also contributed to the film’s soundtrack, including the end song, which he wrote with Mark Ronson and Andrew Wyatt

‘I’m a gamer, and it still took me a few days before I could crack the code,’ he said, explaining he turned to YouTube tutorials for help.

‘It’s kind of like Legos where you build structures and you mine for materials, and I started building a castle on top of a mountain,’ he said, adding it was, ‘Really fun, cool stuff.’ 

Black will also be hosting Saturday Night Live at the end of the week for the fourth time, getting one step closer to getting the coveted fifth hosting gig. ‘I’ve hosted thrice,’ the funnyman said, ‘I don’t want to toot my own horn – thrice,’ he said again rolling his Rs.

A Minecraft Movie opens in theaters Friday.