Mise-en-abîme ("placing into infinity or "placing into the abyss", see Wikipedia) has always fascinated me. I suppose it started with the Quaker Oats man (who I'm sure I've mentioned here before):
Though I remember this image more vividly, and with reds, and I think from my childhood. Notice how he's holding a box with another Quaker Oats man just like him on it, and he's holding a box, ad infinitum.
The laughing cow is another food-related one (see http://lunettesrouges.blog.lemonde.fr/files/2007/10/mise-en-abyme.119332...).
Also popular in the visual arts (Dali's La Guerre, see http://www.ecriture-art.com/art/dalilaguerre.jpg).
And literature (the play within a play of Hamlet, footnotes to a poem in Pale Fire which actually constitute the narrative etc.). And film (Synecdoche, New York is probably the best example, but it also happens in Adaptation and more recently in Inception: dreams within dreams, reflecting and influencing each other).
And obviously in nature and mathematics we have fractals. And in computer science recursive functions. And so on...
So, quite interesting, occasionally mind bending.
I wondered whether I could extend this idea to web servers: could a web server present a page; and on that page, a link which would start another web server and load a page from it; the latter page being embedded in the first page, and also presenting a link which would start another web server then load a page from it; ad infinitum...
So I wrote such a thing in Ruby. It's attached to this blog entry. Here's a screenshot:
It could carry on until the resources of the computer ran out (here I started 19 web servers). It uses jQuery to load the content from the next web server into an iframe inside the current page. You need rack, backports, and mongrel to run it.
Just for fun.