TONS of Cameos/Bit Parts

Filmmakers, actors, comedians, musicians.

The ones I caught were:
Dan Aykroyd
David Cronenberg (director)
John Landis
DeeDee Pfeiffer (Michelle's younger sister)
Rick Baker (make up effects)
Don Siegel (director)
Jim Henson
David Bowie
Amy Heckerling
Lawrence Kasdan (writer)
Jonathan Demme (director)
Carl Gottlieb (writer)