So, when I got home from work on this evening, I went into the bedroom, where I noticed two small roundish things along the side of the wall right where it meets the carpet. Always the curious type, I poked one with a stick. They are ... mushrooms. MUSHROOMS. Seriously, there are freaking mushrooms growing up from inside my wall and carpet.
After some investigation, it appears that the back of my washing machine has been slowly but steadily leaking. The washer and dryer are in their own closet that was built specifically for them, they fit snug, and I've never had any reason to take a flashlight and see what's behind them. Well, not until now, at least. So anyway, the best I can figure out is that the water has rotted the woodwork to such an extent that mushrooms are growing out the other side.
Needless to say, this is kind of disturbing. If the woodwork has become so rotted that it's now actively supporting fungus, I'm lucky the whole floor hasn't collapsed into the apartment below. Maintenance is coming first thing Friday morning.