Two reasons for this odd behavior:
1) They are super curious and want to see what kind of shampoo I use
2) They believe a serial killer might be hiding in there because they have seen one too many movies...
The last party I had, which has an eighties theme, I decided to put someone from the 1980's in my shower.
Because how many people can say they have shared a shower with Darth Vader?
Aside from the Emperor of course...
~The Office Scribe