I thought Reacoom was #16's brother. In the Ocean Dub, Vegeta called Reacoom an "Android" and, well, my young mind went from there.
When I saw the Japanese (no subs) episode of Future Trunks arriving to stop Freeza, I thought Trunks was actually Goku. Why? The part where he says "I'm not soft like Goku" and Freeza saying the name right after made me believe Trunks was introducing himself as Goku. Also, the only Super Saiyan I've seen up to this point is Goku. Oh, and I thought King Cold was actually Freeza. By this point, I've only seen Freeza's first form, and that looked closer to Cold than anything else.
Sometimes I wish I could go back to my original thoughts of things. Mainly because of how funny it was.