You inspired me to actually look this up, and I got some X-Files references, and a few promising Google Books, one of which may well be where CD cribbed the idea from and which describes a cave dwelling visible through a portal that appears in a closet in a room otherwise identical to a real one.
I'm torn between a sort of diaphanous wedding-cake chair with surrounded by blurry, school-disco quality light FX, and a kind of furry dollar sign that two can sit in while being pulled along. A (small) angelic host choir would be de rigour for either.
I think the key idea is likely a specialized space for those who are sufficiently high up the spiritual chain to be chosen for the profound tasks that await and the private but homely closet space reflects that spiritual seriousness. The air of faint ridiculousness that comes with it has to do with the impoverished imaginations that produced the need for it as a cover, IMO, for something far more earthbound.