What if an <iframe> had within it another <iframe> of the exact same source? Inception, as they say. Baptise Crespy does this all-important research in the name of art and science.
Turns out browsers are smart enough to not allow this infinite looping to occur (and likely crash your browser/computer). They strip the content after the 2nd nest. But! If you change the URL of the src to be unique (but still essentially serve the same document), it works. Adding some random colors and animations and things get weird really fast.
Motion warning video:
