Michael Biehn taken out of Terminator 2
Biehn played Sgt. Kyle Reese in the original Terminator, so it was only natural that he should return in the blockbuster sequel, even though he was dead. And that was the plan, at first, in Sarah's nightmare sequence. However, the parts with Biehn were ultimately deemed unnecessary, and unrelated to the main theme of the dream (which was "showing up to school naked" - or, wait, maybe that was just us).