(Cover) - EN Showbiz - Kanye West and Jay-Z sent kids "crazy" when they performed together at a sweet 16 party.

Kanye, who celebrated his 34th birthday last week, surprised a young girl on Saturday night at her extravagant 16th birthday bash.

The American rapper joined Jay-Z and Ryan Leslie at the Carlton Hotel to celebrate the birthday of Leslie Taylor the daughter of Jay's long-time business associate and friend Chaka Pilgrim.

The stars attended the bash which featured Black Swan-themed decor, including human "mannequins" covered in feathers and ballerinas in Black Swan attire.

Kanye and Jay-Z took to the stage at around 11.10pm to sing Happy Birthday to the thrilled youngster.

A source told the New York Daily News that the crowd went "crazy" when the rap royalty pair began performing.

Kanye was spotted "hooking up" with Mary-Kate Olsen last week as he celebrated his birthday at Submercer Nightclub in New York City on Wednesday night. (C) Cover Media