One of my fondest memories because...

Back in college I had this on a homemade VHS tape right after Conan (I was a very young kid when I taped it and didn't realize how cheesy it was). My friends and I intended to watch Conan, but I had to hit the restroom so I give the tape to them figuring I'll miss the first few minutes of Conan (No big deal, I've watched it multiple times). When I get back it turns out they're watching, to my horror, Yor (since VHS tapes end where you stop them, and since I only ever watched Conan, it picked up after the credits rolled). I tell them not to watch it since it's awful, and go to hit the stop button, when they yell at me to sit down since they all found it hilarious. We end up riffing it long before we heard of MST3k. Enjoyed far, far more than if we had watched the movie we were supposed to.

20 years later we can still quote some of the stuff we came up with. I even grabbed the theme off itunes just to let them hear it again. Such fond memories, and all because of a mistake.