Penny found the following Joni mention in the shoot script for Fight Club:
Taking the lectern is CHLOE, a pale, sickly girl whose skin
stretches yellowish and tight over her bones. She wears a
head bondage. She clears her throat.
JACK (Voice Over)
Ahh, Chloe. Chloe looked the way
Joni Mitchell's skeleton would look
if you made it smile and walk around
a party being extra nice to everyone.
Well, I'm still here -- but I don't
know for how long. That's as much
certainty as anyone can give me. but
I've got some good news -- I no
longer have any fear of death.
This Joni mention did not appear in the movie, according to Gerard. He reports that in the film, the reference is to "Meryl Streep's skeleton."
(Contributed by Penny, Gerard Castelein)