A Blue Bowl is a toilet bowl that has recently been cleaned by Plant Services.
Plant Services uses a cleaning solution that is blue. Over time, the denser portion of the cleaner will sink to the bottom, but the overall effect of the blue color will remain consistent throughout the medium.
The thrill of getting a Blue Bowl lies in the fact that this is the cleanest you can possibly have a toilet, since it is guaranteed that you are the first to use it since it has been cleaned. The chances of a Blue Bowl are rare, and getting one is an unexpected surprise.