There is a surprising similarity between the James Cameron's movie "Avatar" and Time for the Stars by Robert Heinlein. Both stories involve twin brothers, one of whom is crippled. Was Heinlein's influence ever acknowledged by Cameron or by critics?
This article points out multiple Heinlein correspondences in Avatar, including Time for the Stars. Cameron has said Alien was based on the bugs in Starship Troopers, so it's plausible that the twin brother idea was also borrowed from Heinlein.
But as @Ward mentions, it's just one point of similarity. Avatar has a wide range of correspondences to many previous works. My favorite is: Greedy human is jealous of nature-adapted blue people, and creates an artificial one as a spy. It rebels against him, saves the day, and becomes a real blue person by magic. In other words, Jake Sully is Smurfette.