Jean Claude Van Damme almost had a very different big break in film; he was the original casting choice to play Predator. They even started production, with a completely different alien design, but Van Damme so vocally disliked being stuffed into the latex suit he was cut from the cast. Kevin Peter Hall took his place and the alien was completely redesigned (probably because it was originally designed by someone without FX background and was, by all accounts, not working). Because the redesign resulted in such an icon, every effects artist working at the time now claims to have had a hand in influencing the look of the Predator. James Cameron even claims he casually mentioned to Stan Winston (who's team of artists actually did the redesign) that he'd like to see a creature with mandibles.
Like all stories about classic movies, we'll never know who said what to ultimately inspire whom. Though, you can usually rely on stories from players that didn't make the annals of history. Here's a clip from the recent webcast by Stan Winston School of Character Arts (SWSCA) featuring Steve Johnson discussing that original Predator design and how he insisted it wasn't going to work, only to be proven right.