When I was younger, my dad, sister and I got stuck on Big Thunder. It just came to a screeching halt of a sudden and a few people got slightly banged up, but we were all fine. I was probably about 10 at the time, and walking through the mountain was probably one of the coolest experiences I could have imagined.
A few years later I got stuck on the new Imagination for about 10-20 minutes. They never evac'ed us, but the music just kept going. I still shudder when I hear it. My wife had a similar experience on IASW, between two of the scenes so she was getting the song in two different languages. Needless to say, it's tough getting her back on it!