Cyrus, 27, has been keeping her 105 million followers entertained with her Bright Minded series, a comforting talk show aimed to distract and reassure viewers during the coronavirus outbreak.
While the series has seen big-name stars such as Demi Lovato and Rita Ora appear, fans were the most excited by the appearance of Osment, 28.
Teasing viewers they were “gonna be shooketh”, Cyrus told fans: “This is the reunion of the decade. My BFF that shared the screen with me for the last 15 years.
“On and off screen, she’s been a badass best friend.”
Osment starred alongside Cyrus in Disney Channel teen sitcom Hannah Montana for five years. Cyrus, 27, played the titular pop star while Osment, 28, portrayed her best friend Lilly Truscott.
The pair spent the episode discussing their time on the show, last on air nearly a decade ago, and decided to embrace their wacky on-screen personas, recreating the show’s “sanitising” scene.
“There’s a theory the show predicted everything that was going to happen in life,” Cyrus joked, as the world is currently exercising increased cleanliness to combat the spread of coronavirus.
Osment and Cyrus also discussed how they felt about filming Hannah Montana as they got older, saying it felt “strange” dressing up in the same way they did when they were younger.
“As we were starting to get a little older, I remember it kind of feeling a little strange to put on a tutu and a wig,” Cyrus said. “They say you get younger as you get older. Now I put on wigs and dance around the house.”
Bright Minded, which discusses how to ‘stay lit in dark times’ continues weekdays on Instagram Live.