Check out the Talk for the real truth behind this glitch.
This truly happened. Whether you believe me or not, this is the scariest thing I've ever seen and heard. It was the start of my Pokémon Yellow Game on my computer (Windows 7 Home) and I decided to enter some GS codes so I could force Prof. Oak to fight a MISSINGNO instead of the usual Pikachu. I thought the result would be funny. To make it more fun, I also hacked around with the memory.
The game loaded and I started a new file. I skipped Professor Oak's speech. I named myself AAAA and my rival got the same name. I wasn't bothered to choose real names for them as the game would probably crash anyway. I lead my character out of the house and towards the grass. I stepped into the grass and Prof. Oak's theme started to play.
OAK: Hey! Wait! Don't go out!
My character noticed Prof. Oak's presence as he came rushing towards me.
OAK: That was close!
Wild POKéMON live in tall grass!
Oak turned to the right as a battle started. That's when you usually face Pikachu, but oddly, the screen remained black when it was supposed to fade into the battle screen. The battle music played normally before changing. It started to sound choppy, but it kept going. Then, out of nowhere it changed pitch in a frightening manner. The battle screen finally showed in, greeting me with choppy pixels fading in as prof. Oak's opponent.
When the animation stopped, I could swear I could hear Pikachu scream in sheer terror. My heart was pounding. The game screen got covered in a weird pixelated pattern. Both, Oak and the pixelated something were glitched up as well.
The sound then cut to static noise as the corruption became worse, Pikachu's screaming heard in the background before it became silent out of all sudden. No static or screaming. After a few seconds the screen changed again, now just being black lines on a white background while a dull sound repeated itself, sounding like slamming or gunshots. That didn't last for long before the slamming stopped and the game made glitchy noises. Some of the screen was suddenly taken over by that odd pattern again.
It looked like a H and a K right next to each other. HK. The game was silent and I thought it finally crashed. The pattern flickered and some of the screen became green and black. Just as a second passed the screen now was a glitchy mess I can't even describe. Static played again before I heard Pikachu scream once more. Statics. Slamming. Glitchy noises. In the end there was a noise that dropped in pitch.
I finally grew sick of the game and closed the emulator. Ever since I felt sorry for what I did..