Mario and Fergie appeared to be channelling the Victorian era as they dressed up in formal attire complete with wigs!
A young Mario looked dashing in a blue jacket and white ruffle collar shirt, while young star Fergie was all smiles as she proudly posed with a handheld paper fan.
Mario posted the photo on Twitter yesterday (21 November), as part of the site's weekly 'Throwback Thursday' trend.
Captioning the snap, he said: "#TBT the Dutchess @Fergie before she was the 'Dutchess!' Don't know what the heck I was... #KidsIncoporated."
In Kids Incorporated, Fergie played the lead character while Mario was one of the dancers, and the show was where Mario and Fergie shared their first kiss!
The pair actually enjoyed a brief childhood romance and have remained the best of friends ever since. In fact, in 2009, Mario told People: "I'm happy to say Stacy has stayed just as sweet as when we were kids. I'm happy for all of her success. She deserves it." Aww!
Now Mario, who catapulted to fame in popular 90s show, Saved By The Bell, is host of US chat show Extra and presenter of US X Factor. The 40-year-old, who is married to wife Courtney Mazza, has two children - three-year-old daughter Gia and baby son Dominic, who was welcomed September this year.
Meanwhile, Fergie, who is a chart-topping solo artist and star of the Black Eyed Peas, welcomed her first child, baby son Axl, in August with husband Josh Duhamel.
Check out more stars who became parents in 2013:
Copyright: Love & Lust London