Hubby pointed out the illusion of the fish in the tank in the hospital waiting room. Viewed straight on you would see four fish. Viewed directly from the end you would see that there are four fish. Viewed at the corner, you see each fish twice--well, except for that one at the bottom which you barely see peeking around the corner on the left (and you probably missed if you came up with an answer of seven).
If you saw five, you probably missed the dark one in the bottom altogether, and the one circled in blue on the left hardly looks like a fish.
I think it's odd that the one circled in red seems to be in exactly the same pose from both angles.