Grab the mic to the full dorm adress system and yell about your haunted house. Maybe a very creative, scary voice, sound defect or phony news bulletin first to get everyone's full attention?
Sure. This will work.
Shimer College used their full dorm address system to fill out their basketball team on game night:"Attention! Anybody know how to play basketball? Come on down here and try on a uniform!"
(And that is how they now hold the small -collegiate record for the most continious losses ever! I got to see some of those games! It was HYSTERICALLY ENTERTAINING and memorable!)