I have probably seen the first Star Wars film (Episode IV by George Lucas’ count) a dozen times or more, but I had never noticed the hidden sauropod in it until Matt Wedel of SV-POW! pointed it out. While the android C-3P0 wanders around the desert at the beginning of the film, the bones of a large, sharp-toothed creature can be seen in the background. The head is a Hollywood invention, but the vertebrae are casts of a sauropod skeleton.
More prominent were the Rontos in the “improved” special edition of Star Wars that came out in 1997. They are obviously sauropod-like, but what I didn’t know was that they were derived from the already-existing computer models of the Brachiosaurus seen in Jurassic Park. Matt has all the details at SV-POW!