Nekojin: Actually, the bicycles are most likely a sign that the people at the door were Mormons (who rarely use cars in their missionary work) rather than Witnesses (who usually do, though for no particular reason).
And a note to those who try to come up with funny ways to scare Jehovah's Witnesses off: they find your methods just as funny as you do. Don't do anything you wouldn't mind having strangers talking about (and most likely laughing at) for quite some time. My mother, who's a Witness herself, has quite a few interesting stories to tell, like the time she was out with her mother and some guy came to the door naked. My grandmother's response: "Hey, this city witnessing is some interesting stuff; I should do this more often..."
My favorite one, though, comes from a friend of mine. His martial arts instructor (I don't know for certain which art, but I think it was kenjutsu) is a pagan; specifically, he worships household gods. Anyway, one time he and his brother were practicing in their basement, with the instructor's son watching TV upstairs. Someone rang the doorbell, and the kid goes to answer. The conversation went something like this:
Evangelicals: Hi. We're here to talk to you about God.
Kid: Which one?
Evangelicals: Well... um... the Christian God, the One God...
Kid: Oh. One sec: (Turns to the basement, shouts) DAD, THERE'S CHRISTIANS AT THE DOOR!
Instructor: (Shouts from basement) Oh really? What do they want?
Kid: They want to talk to you about their god.
Instructor: Oh. One sec...
At this point, the evangelicals are greeted with the sight of the instructor and his brother, still dressed in full ceremonial armor, along with their two dogs -two huge Irish wolfhounds- which had been in the basement with them. They enter the house (this is the clue that they were Mormons; a Witness will never actually enter a house unless invited, and even then usually not on the first visit, preferring to instead schedule an appointment at some later date so they can return to their door-to-door activities for the day).
The evangelicals say a short prayer once inside. The instructor says that this is fine, but that now his family has to pray too. The evangelicals agree to this. So the instructor and his family break out the incense and decide to have a little fun. So they start in on the sacrifice prayer from Conan the Barbarian. They get through the first four words:
"O serpent of darkness..."
At this point, the evangelicals freak. This spooks the dogs. They're trained not to actually attack, but they start circling the couch menacingly. The evangelicals climb up onto the couch, throwing books at the dogs. This doesn't help. Eventually they manage to run away screaming and bolt off. Supposedly no evangelicals have visited them since.
I don't know if this is quite true, though I have no reason to doubt it. But Mom got a real kick out of it.