Lil Uzi Vert Shares Stage with Meek Mill Son Papi at Philly Concert .

Lil Uzi Vert brought out a special guest Friday night at his Philadelphia concert ... Meek Mill's son.

Uzi called Papi to the stage as he sang "Dreams and Nightmares" to the crowd on his last stop on his XMAS tour.

Papi had to share the spotlight with other special guests, including Nicki Minaj, Pharrell and A$AP Ferg.