Watch John Mayer And Dave Chappelle Cover Nirvana In LA

John Mayer has appeared on Chappelle's Show before, and on Tuesday night, Dave Chappelle returned the favor, showing up at Mayer's secret acoustic show in LA to sing a few songs. Chappelle's love for Nirvana is well-documented, and he proved it again at the concert, assisting Mayer on a cover of Nirvana's "Come As You…