I think that a crime scene of any type may draw unwanted attention.
I like the alien pregnancy thing. You could make it work if you used a big plasic bag with an alien puppet inside, and a lot of red-dyed water. The actress wears a rig to hold it up on her belly, maybe concealed within a full-body costume. Her “husband” can rush to help as she goes into her fake labor, and after practice he could pull the “alien” out and over his face, as if it was attacking. Have someone else on a cell phone, pretending to call 911, so that no one tries to “help” that way. It’s weird enough that people will get the joke right away and not go into hysterics (like if someone was murdered before them), after the initial shock. Make sure a picture of the crowd is taken as the “baby” is born; if you have a digital camera, computer, and good printer you could give prints as party favors or mementos.
So if you have a house party where you know a lot of people you do a sort of “Secret Horror” sort of thing.
You and your bud/wife/cohort leave the party together–whether you go upstairs or outside–it has to be somewhere where regular party guests wouldn’t go. Come back a few minutes later with blatant looks of horror on your face. Whisper things to each other and try to quietly, but animatedly, calm each other down when you return to the party. Keep looking out of windows and around corners.
If someone asks you what’s going on, just deny everything, say you can’t talk about it and so forth. Then pick somebody and both of you leave with them. Get them in on the plan.
After a while, everyone looks either confused or terrified. Always leave a few people wondering what the hell is going on.
Then have a few people run through the room screaming and all the other folks you “showed” your nasty secret will also scream hysterically at randomly selected times during the night…
You people are awesome. You’ve given me some good ideas. We really want to do the pregnant belly one, but I don’t know if we have time to get ready for it.
Whatever we decide, I’ll post it (and pictures if possible) here. Keep the ideas coming though. There’s no reason we can’t pull off several of them.
