I remember exactly two occasions where the Mandelbrot has been seen in meat-space.

One was a mention on Slashdot:
http://science.slashdot.org/comments.pl?sid=1444562&cid=30110928

"I found that hot chocolate (not too watered-down) in a white ceramic mug leaves a very rudimentary but easily discernible "Mandelbrot" set. At least the classic image (I have no way to zoom in to great detail on the side of my mug.). The set is left over from "chocolate bubbles"."

The second is in reference to magnetic fields from this page:
http://www.miqel.com/fractals_math_patterns/visual-math-mandelbrot-magic.html

"Also Mandelbrot curves have been discovered in cross-sections of magnetic field borders, implying there is a 3-D mandelbrot equivalent that is closely tied to electromagnetism and therefore a deep structural and fundamental aspect of life, and physical space/time."

Are there any others?

I think they just see the classic cardioid that can be seen due to reflexion of light on a cylindric surface. Look at your cup of chocolate (or coffee, or anything else...) under a strong light...

Lol, do you think that's all it is? I can't imagine how he'd mistake it for that, because all one would have to do is move the cup slightly and the cardioid pattern would change drastically.


Yes agreed. I asked him for a photo actually in my reply. No response.

I think (I hope?) he's just making a joke.  The Slashdot crowd is always full of wise guys.  I was a regular there for several years but kind of got bored with it.

If he's not joking, then I agree, he probably just saw an odd reflection.  Or, he's been staring at the M-set for too long (like me) and now every time he sees two circles touching each other, his brain tricks him into seeing the M-set.