The following is a true story that happened to me around three times, and will always confuse me.
Up until 2000-2001, there was a software company called Berkley Systems. They were best known for their immensely popular screensaver programs called Afterdark, and the game, You Don't Know Jack! One of their most popular screensavers in their packs was Bad Dog! This was a funny one about a dog who would tear your wallpaper, pee on your trash can, dig holes, and do more to your desktop while you idle. They also had one in AfterDark 3.0 (or 3.2?) called Boris, about a cat who did cute, catlike things on your screen. These screensavers were very vivid, had great MIDI effects, and always will be with me to my dying day. They were a huge part of my early days, to say the least. If you started Boris, occasionally Baddog would come in and chase Boris around for awhile.
This would have different animations and sounds than the rest. The same happened with Bad Dog!, where you would have Boris come in, and get chased. The first time the mysterious black screen happened, I was around 3, and was interested, but terrified of it. The black screen was very rare, even more so than the invasion of Boris. What happened, was that instead of your background, there was a jet black screen, with only BadDog on it. He would stare into the distance, bristling and growling for awhile, periodically whimpering and running offscreen, just to sprint back on seconds later. This had me terrified. I was always wondering what horrors lay beyond the blackness, that only Bad Dog could see. Needless to say, the other times were equally disturbing, and to this day, I'm still haunted by the creature beyond the blackness.