Get a met balloon and and eletric squib. Fill said met balloon with powdered chalk and blow up to considerable size. Take a view foil frame (remeber those, things before Powerpoint!) cover both sides with tin-foil, gently blow in the middle to balloon it out slightly and seal. Hey presto, instant pressure pad!!! Connect the squib through the pressure pad to a 9v battery and attach to balloon. Close curtains, take light bulb out and place pressure pad inside the door.
Add in the other effects, fish, cress carpet and porn wallpapering etc...
Sit back and wait for the bang!!!