Jeff Goldblum Met Ariana Grande 20 Years Ago, but Totally Forgot

Jeff Goldblum Ariana Grande, Who??? Drew a Blank on Their First Meeting 20 Years Ago

"Wicked" isn't the first time Jeff Goldblum and Ariana Grande have crossed paths ... with the veteran actor confessing he met the pop star 20 years ago -- but totally forgot all about it.

The "Jurassic Park" alum swung by "TODAY" Thursday, where he opened up about working with the Grammy winner on the musical movie ... and revealed they actually go way back.

Jeff says halfway through the making of the big screen adaption of "Wicked," Ariana reminded him that they had actually met in NYC once before ... though, she was a little girl at the time.

Ariana and her mom, Joan Grande, waited backstage at the Broadway production of "The Pillowman," in the hope of meeting Jeff, who starred in the play at the time.

The mother-daughter duo got their wish, too ... as pictures show Jeff mingling with the crowd, even giving the young Ariana a hug.

While the moment was a memorable one for Ariana and Joan, Jeff confessed he "hadn't remembered that" ... which is fair since he was greeted by hundreds of fans every night post-show.

Though, Jeff will remember Ariana moving forward, praising his "Wicked" costar to Savannah Guthrie and Hoda Kotb as "fantastic."

Ari may already be a global superstar, but she's set to get even more "Popular" thanks to "Wicked." We caught up with the singer out in NYC this week, where she was swarmed by fans clamoring for autographs ... making it clear "Wicked" fever is upon us -- it will be shocking if the film doesn't dominate the box office!!!