Funny story. I had a bunch of tracing paper + a how to draw pokemon book, and this annoying kid wanted to draw something, but there was only a limited amount of tracing paper, so I didn't let him. However, he had a tale of a mysterious pokemon, and that he would tell me if I let him. I had him draw the pokemon, and since it was a tetris-block, it seemed unbelievable.
This kid was a compulsive liar, so I passed this missingno off as another one of his stupid lies. However, a couple months later, I went to my cousin's house, saw that he has a pokemon that looked like a tetris block, called missingno, and I was in awe, starting my obsession (just take a look @ my username