Every once in a while, Buster will wake up from a deep sleep and start half-heartedly barking (or "Boofing" as it sounds) at a random corner of the room. The only explanation I can see is that he's scaring off a ghost who's wandered into the apartment by mistake. I can't recall being haunted in the recent past so he must be doing a pretty good job. If someone has a better theory, I'd like to hear it.