Yeah, it was a bit confusing - what Rodney really said was that he had traveled to another universe himself once, and had met another John (and maybe another Rodney?) there. Which seems to be what inspired him to seek & study the John of his own universe, when he got back.

This was one of SGA's better writers so I don't know how they would've pulled off a whole season of genre-parody, but it would've been fun (I'd love to see a show like that, about the same set of chars in different universes...was just pitching it to the sibs, actually! ^^)