I’m generally a fan of a good optical illusion, but some get so overdone. There’s pictures you’ve seen a million times, which line is longer, etc, and you just know what to expect.
You then go one step up to things like this, which manage to move without moving – harder to get your eyes around, though I find if I blur my eyes, not only does it go still, but it also goes black and white?!
But 2 or 3 years ago there was an episode of QI that blew my mind all over again, and still does when I watch it afresh!
Then last night I saw this, along the same lines but almost a step further
I seriously don’t get it – I’ve been wearing glasses for over 20 years now and I’ve seen all sorts of tests, but this is bizarre. It’s the sort of trick that when it’s happening you literally can’t see how it’s doing it!
ineke.co.uk 
The T-Rex is fantastic!
There are a few illusion videos like that, either using an inverted form like the T-Rex or projecting a pattern onto a blank surface.