< Ok, let's try again.. (my last writeup on this got eaten - deservedly, I might add). I just feel it is unfair to link to a node with a neat and intriguing name like "folie a deux", only to find nothingness. >

Folie a deux is a term for a delusion shared by two people (there is also folie a trois, folie a quatre, etc. - you get the idea). There are several criteria that have to be met for this designation to apply:

There was also an X-files episode titled "Folie a deux", involving a paranoid vinyl siding telemarketer who ran amuck. In the episode, Mulder started having paranoid hallucinations as well and was committed to a mental institution. As it turns out (conveniently) Scully discovers that a creature is injecting some kind of toxin into Mulder, who makes a full recovery. Very "deus ex machina". It is also the name of an X-file fanzine on Yahoo!

Last (of the things I know of) but not least, especially to wine connoisseurs, it is the name of a Napa Valley winery which was founded by two psychologists. Not being a wine drinker, I cannot personally vouch for the quality of their wine, but it is reputed to be good.