I don't get it
Please don't take this the wrong way, but that was a very poorly conceptualized Flash. I did like some of the obviously traced and reused running sequences with the bizzare pasted on heads. I also thought that the gloopy water effect was impressive. Overall, however, I found this to be extremely disjointed.
For one, the music goes berzerk between action sequences. The songs come to a complete halt and start up without warning. It's a pretty jarring effect, but if it was an intentional design issue I urge you change it.
The backgrounds really need to be done directly in flash as opposed to being imported JPGs. The reason I say this is because the movie is gargantuan in size for as long as it lasts. 10 megs??? around 2 minutes??? Unacceptable! I know you probably like the nice photoshop textures, but I really can't justify anything that causes to file size to swell so needlesly. And your lines are thick to the point of being distracting.
Lastly... what the hell is even going on with the title? There are some space cadet kids running through the halls and a guy cleaning what appears to be chicken broth off of a toilet. I can't fathom how this got the name "Janitor Massacre". It just makes no sense.
Critisisms aside, It had a cool look to it and I think it would be worth continuing. Maybe do up some storyboards beforehand, it couldn't hurt.