Watch Red Hot Chili Peppers guitarist John Frusciante sing Spinal Tap's Tonight I'm Going To Rock You at chaotic 1991 Los Angeles club show

In autumn 1988 Red Hot Chili Peppers recruited 18-year-old New York-born guitarist John Frusciante as their replacement for Hillel Slovak, who had died as a result of a heroin overdose that summer. At the time, Frusciante had just started playing with cult LA punks Thelonius Monk, fronted by local scene legend Bob Forrest, a long-time friend of Chili Peppers founders Anthony Kiedis and Flea, who gave the young guitarist his blessing to take the opportunity he'd been offered, despite the loss to his own band.

Frusciante never forgot Forrest's kindness, and the two musicians remain good friends to this day. In October '91, shortly after the release of the Chili Peppers' 'breakthrough' album Blood Sugar Sex Magick, Frusciante, Kiedis and Flea popped in to Hollywood venue Club With No Name to catch a typically raucous Thelonius Monk show, and Frusciante was persuaded to take the stage to supply vocals on a cover of Spinal Tap 'classic' Tonight I'm Going To Rock You.

Frusciante's delivery may be a little... wayward, but no-one could doubt his commitment to the song, and what his performance lacks in subtle melodic nuances, it makes up for in terms of enthusiasm and energy. Frusciante once spoke approvingly of Bob Forrest singing as if he was trying to burst out of his skin, as if his soul could not be contained within his human frame, and so the vocalist doubtless appreciated his efforts here.

Watch the clip below:

In later years, Bob Forrest, a recovering drug addict himeself helped Frusicante deal with his addiction problems: he now works as a recovery advocate and is the co-founder of the Californian rehab facility Oero House Recovery Center.

Forrest and Anthony Kiedis founded a TV/film production company earlier this year, and are currently developing an animated TV series, Hellicious, based on the comic book of the same name, for US cable TV network TBS.