I liked all of the ridiculously elaborate conspiracy theories in the original Pokemon games. My favorite was the secret of Bill's backyard: remember Bill, guy who lived in the two-tile-wide house at the very top of the map, north of the gym where you fight Misty (vermillion city?), which had a two-tile area of normal ground in the cliff that was blocked off by Bill's house? The rumour that I heard was that, if you beat the Elite Four ten times in a row using the same selection of pokemon (I think you might have not been allowed to use ones in particular slots, though I don't recall for sure) and without speaking to anyone or going to a pokemon centre, if you went immediately to Bill's house, there would be a new door in the back wall that would allow you to walk to the two-tile backyard, where one of the random encounters was Mew, who you could catch.
Obviously bullshit, though that isn't to say that I didn't try. The best part was that the ridiculous, convoluted process to find MissingNo and duplicate your items, which actually did work, made all of these theories credible.