Well, I did a little research and came up with a glitch in Pokemon Platinum. Apparently, if the glitch is very bad, then walls in the Underground may collapse. Like, everything. Here's a story I found. Reader discretion advised: http://fyeahpokemoncreepypasta.tumblr.com/post/1714939190/buried-alive
I'm pretty sure that all the walls collasping is a realistic glitch, but I'm not so sure about the corpses thing.
*EDIT: Well, as you may have concluded from the comments below, the glitch in this story isn't real. Yeah the collasping underground thing was pretty convincing, but, it's completely fake. There may still be a buried alive glitch though........but I doubt it.