Mariah Carey got free entertainment from a rapper/panhandler -- but it was only free because she stiffed the guy's request for money afterward ... in classic Mariah fashion.
Mariah was holding court outside Mastro's Steakhouse in Bev Hills ... swarmed by paps as she floated to her ride, and you've gotta see what happened once she got inside.
Watch for the bald guy who squeezed through the crowd to get right up to Mimi's window. His performance was awesome, and her reaction is hysterical.
Mariah's biggest mistake -- she shoulda signed this guy to her band!