The "Stranger Things" and "Dance Moms" stars shared a video, along with their friend Lilia Buckingham, as they first rocked out to Ariana Grande's new song, "Thank U, Next," until Ziegler lost her balance and tripped backwards into a door.
Then they switched it up by singing the Spice Girls classic hit, "Wannabe." It was announced this week that Mel B, Emma Bunton, Geri Horner and Melanie Chisholm are going back on a reunion tour. Victoria Beckham opted out, but sent her well wishes to her former bandmates.
As for Millie and Maddie, there's a very good chance the girls will be at multiple shows during the tour.
BTW, "Wannabe" debuted June 26, 1996 ... and both stars weren't born until the early 2000's.