Echosmith Are 'Thinkin' About Somethin' With Hanson on 'Greatest Hits'

Sydney Sierota gets a little flirty on stage while performing on ABC’s Greatest Hits, which aired on Thursday night (July 7).

The 19-year-old Echosmith singer and her brothers, Noah and Graham, hit the stage to perform with Hanson on the limited series.

PHOTOS: Check out the latest pics of Echosmith

After performing “Thinking ‘Bout Somethin’”, Hanson treated the crowd to 1996′s smash hit, “MMMbop”.

“Filming something fun today w/ @hansonmusic @ArsenioHall,” the band shared on Twitter after filming a few months ago.

FYI: Echosmith is wearing head to toe AllSaints looks for their performance.