Haunted houses for impromptu Crawlspace sessions are like cheese dips at parties, very popular and easy to handle, if full of potential trips to the hospital. Besides having a matrix for developing these scenarios, I avoid having to worry too much about the roles of the Characters by making them a part of a reality TV show. This way the players, err Actors can essentially be themselves or not without me having to come up with back story for them. The players have to decide their roles, or an Open Draw will decide for them.
Camera- Though everyone and his brother has a camera on their cell phones, this is the dude, or gal, that insist on carrying a shoulder-carried "professional-grade" camera on his shoulder. This better photographic quality gets to show the Talent's faces as they react to stuff that he is not filming.
Tech, flunky- This is the guy that gets to put up all the stationary cameras, run cables, fill up the van's tank, get coffee and sandwiches, etc... etc.
Tech, master- This guy, because of his mastery of owning a van, gets to run the "control" area.
Talent, big shot- This is the biggest ego, err the star of the group. Usually the one finding cold spots next to air conditioning vents and electrical spikes next to power lines.
Talent, putz- This is the guy that has his cell phone camera out. Then he always gets scared and just misses filming whatever just scared him because his cell phone camera was on him looking scared.
Talent, color- Usually known as the "psychic" or the "empath," but can be a special guest like a site historian or someone once involved with the place.
The GM/Director starts everyone back at the studio and then the team gets a call. This will be a lead to a site. The type of area depends on a Draw:
Ace- An abandoned centuries-old mansion next to a cemetery (+2 for encounters).
King- The site of a murder or an fatal accident (+3 for encounters).
Queen-Jack- An old house with a well established family living there (+1 for encounters).
Ten-Seven- An old hospital or a farm with a large house and stables and a barn (picturesque but no bonus).
Six-Three- An apartment complex, motel, restaurant, or a strip-mall
Deuce- A store or a fast food joint.
Joker- Draw again for locale but guaranteed encounters.
Once the gang is at the scene, the GM Draws for possible encounters:
Nine-Four- An encounter that can be explained through regular means, but who wants to do that?
Three- Black card equals one encounter. Red card equals two encounters
Ace- Hearts equal a near complete apparition needing a favor, but it cannot speak directly. Clubs comes to wailing noises leading to clues to a murder. Diamonds moving items protecting hidden moneys. Spades an evil entity looking to kill someone or somebodies.
Joker- A random Ace and two other cards.
Types of Spirits encountered can determined according to the "Spirit Combat" rule on page 25 of the Crawlspace Deluxe rule book. A crafty Director can color things with another draw:
Three-Ten- An indigent Indignant ghost.
Queen-King- A Resident ghost that is easily researched and identifiable.
Ace- "The Infernal," see page 29 of the rule book.
Deuce- The Infernal posing as another kind of spirit.
Joker- A spirit that was killed by one of Characters playing in the session.
The impromptu plot can last for as many Drawn encounters as needed to make the night a complete session. Heck, I've had one that never saw a chair move, but the players kept things going for six hours. A haunted house or a haunted area can be very specific as well, but that varies from site to site. More on that later.