I also thought the Stormtroopers were robots at first. Honestly, even though The Clone Wars were mentioned by Obi-Wan, it never occurred to me that they were clones at all until Episode 2 came out.
For many years we pronounced the name of Vader's command ship as "Ex-e-QUOO-ter", until we realized there is no such word and it's really "Exec-ya-ter".
Always firmly believed that the trench that ran around the Death Star's equator was the trench that the fighters flew down at the end of SW. Was years later when I noticed that the graphic during the briefing indicates that it's a smaller trench that actually runs vertically up the surface instead of horizontally.
It was comparatively recently that I realized that the big, triangular object in the walkway of the Lars garage was Luke's T-16 Skyhopper!
When Time magazine released the first picture of Yoda (in that now familiar still of Luke sitting on the ground beside him), my brother and I didn't realize that Yoda was just short, we thought his legs were simply submerged in the swamp and that Luke was just sitting on the ground at the edge of it.
When I saw "Jedi" for the very first time I thought the Emperor's initial reaction was one of fear after Luke proclaimed himself a Jedi. Up until the point where he said, "So be it...Jedi." that is. At that point I just thought, "Oh, ****, here it comes!" :lol