Rapper Kanye West has taken aim at his girlfriend Kim Kardashian's ex Ray J by branding him "lame" and questioning his manhood during a surprise U.S. TV performance on Monday night (09Sep13). The Stronger hitmaker made an unannounced appearance on Late Night with Jimmy Fallon to play his new single Bound 2 with music veteran Charlie Wilson, and he used his stage time to take a subtle jab at Ray J at the top of the song. However, West stopped short of mentioning the One Wish singer by name - instead, he namechecked Ray J's only sibling, R&B star Brandy, to make it clear to fans who he was referring to. Before launching into his first verse on Bound 2, West unveiled a new couplet, spitting, "Brandy's little sister lame, man, he know it now/When a real brother hold you down you supposed to drown". West and Wilson were backed onstage by presenter Jimmy Fallon's house band, hip-hop group The Roots, and in a subsequent post on Twitter.com, drummer Questlove revealed the rapper simply called him and asked to perform after touching down in New York, where the show is filmed. Ray J famously featured in a 2003 sex tape with Kardashian, which leaked online in 2007, and recently courted controversy by releasing the song I Hit It First, reportedly about the socialite, who gave birth to West's daughter, North, in June (13). On the track, he sings, "She might move on to rappers and ballplayers/ But we all know I hit it first.../ I had her head going north and her a** going south/ But now baby chose to go West.../ No matter where she goes or who she knows/ She still belongs in my bed." The single's cover art even featured a pixellated photo of what appeared to be the reality TV star in a bikini, while a Kardashian lookalike was chosen to star in the accompanying video.