Good luck figuring this one out. Count the number of men in the picture, wait for it to change then count the  number of men again. Where does that extra guy come from?Nice Admin.  
LET me begin like that, I think...
When it changes from 12 to 13, man1 remains non replaced.(it has half-head when the number is 13).And man2 is replaced by man4 from it's own group and man3 is replaced by man 5, again from it's own group.(man3 has shorter legs when tne number is 13). And vice versa.Yeah I came across it recently during my websurfing and thought I would posted it. It really BLOWS my mind and I still have a hard time understanding it.  :-?

I was even taking screen shots of it and trying to compare.  :-/

Still confused even after your helpful description.Download gif animator and take a deep look frame by frame. Here is the free trial(1.1MB). It is really helpful.
http://www.seltecodownload.com/bsga.phpTECHNO ... thanks for the "baby sitter" ...
my husband has been sitting in front of the computer screen for 20 mins staring at the picture!  Hehe. That's PRETTY funny. I feel the same way as your husband, not sure how long I spent looking at this, but I'm sure it was also a good 5-10 min.Another crazy optical ILLUSION animated picture I recently came across for everyones viewing pleasure.

http://www.patmedia.net/marklevinson/cool/cool_illusion.html..... thank you!

Do you realise if if look at it too long ( accidently of course ) then you continue to see circles of green dots right in front of you!