Alternate Casting...

We all know that many Star Trek characters were not played by the actors originally considered. For instance, James T. Kirk was originally offered to Jack Lord (Hawaii 5-0) and Lloyd Bridges (Sea Hunt) befor it went to William Shatner. I recently read that the role of Berlinghoff Rasmussen, the time-travelling con man from TNG was written for the late Robin Williams, who committed suicide this month. I've been a fan of Williams ever since Mork and Mindy (and don't hold it against him for that show destroying the TMP Klingon uniforms). He would have given us a very different, more manic, version of the character than Matt Frewer's (Max Headroom).

RIP Mr. Williams.

I just read this as well. I would love to see Robin Williams as that time-traveling miscreant. Don't get me wrong, I thought Frewer did a fine job. Robin Williams would have made it even better. :)
That reminds me of another alternate casting: in the TNG Episode "The Most Toys," Kivas Fajo was supposed to be played by David Rappaport (of Time Bandits fame), but he committed suicide prior to completing that role. That's why Saul Rubinek got the part instead.
mactavish out.

Of course the other obvvious one was that of the XO on DS9. Who was originally planned to be Ro Laren who had clearly returned to Bajor and her Starfleet Training propelled her to a lofty rank... But Michelle Forbes had other commitments.

How different that would have been... And I notice TPTB have mad this a reality in the DS9 relauch novelisations.