What Could Have Been : Jodie Foster turned down the role of Andie. Anjelica Huston and Tracey Ullman were both considered for Iona.
Word of Gay: Both Molly Ringwald and Jon Cryer have agreed that after high school, Duckie came out of the closet and is currently a Hard Gay, wearing no shirt and suspenders and attending Gay Pride events. Could be considered Word of Dante, of course.
Keep in mind, though, that John Hughes originally wanted Andie and Duckie to end up together, so this is not really Word of God.