I agree with you. I'm a huge fan of improv and I find that the skill truly makes for a great character. It is very obvious to the patrons if an actor is using canned dialogue, especially if they go through the haunt again and witness the same performances each time. Improv also enables the performance to be interactive, as opposed to making the customer feel like an audience at a play.
Originally Posted by NightmareOnYourStreet
With semi-scripted haunts, I find that giving the actor the basis of the character (ex. Doctor, nurse, hillbilly) and allowing them to create the character (name, age, background, dialect, quirks, movement style, vocal pattern, etc) really allows the actor to feel that they contributed and creating something truly unique.
Admittedly I'm a huge of changing things up, and I like switching actors up because it means the show is never the same (which means that the actors aren't bored and neither are the customers). It also allows actors to work with a variety of acting styles (ex. crazy in an insane asylum, a slow and stupid zombie in a morgue, heavy dialogue in a Victorian parlor, loud and violent in a slaughterhouse). I think improv and the ability to change things up constantly is the best way for actors to grow and improve their performances.