A fun janitor is any person who takes a fun situation, and dulls it down. Either by forcing people to focus on a different, less-fun task, or by ruining their good time altogether.
Being a fun janitor is not a good thing, and it implies that you're "cleaning up the fun" or "sweeping all the joy in life under the rug".
Don't be a fun janitor.
**Creation of this original term is credited to Ryan P., who lives in a tiny mountain town of Colorado**
1 - Man, we were having a good time till the boss showed up. She's such a fun janitor.