There was a longtime urban myth that Susan Olsen went into porn. I don't know if it's true or not, but I suspect that it was started by Mike Lookinland. He knew that Eve Plumb was too prude and Cindy would be a better target for the pedophilia. Greg was too busy dating Carol to care, and Mike was too busy dating Sam the Butcher to care.
And as for the cunt Marcia? "It's always Marcia! Marcia! Marcia!"
Allegedly.