Doppelganger - S4-E4
Corrected entry: When Dr. Jennifer Keller is talking about her dream (basically re-telling the scene from the movie Alien when the parasite came out of the body of Teyla Emmagan), Ronon Dex says, "It sounds like that movie," referring to the movie Alien. He did not come from Earth and yet he knows already about Alien the movie. Sure, Lt. Colonel John Sheppard could have told him about it, but it seems curious that he just recalls it so vividly without ever seeing the movie.
Correction: By season four Atlantis is no longer cut off, Daedalus makes regular supply runs from Earth. Ronon has doubtless seen dozens of movies by this point.
Grumpy Scot