How Sweet!  Frankie Antonelli is a teenager with Down syndrome. He was performing a song in his school's talent show in South Carolina, when in comes Darius Rucker!

Frankie was singing Darius Rucker's song 'While I Still Got Time". Towards the end of the song Darius walks on stage and joins in on the singing!

Look for Darius to stroll in at the 3:13 mark.