Now you see it, now you don't!
If you draw and cut out a lion and stick it onto a pencil, and then stick a cage on the opposite side of the pencil, you can spin the pencil so fast that it looks like the lion is IN the cage.
When the pictures spin very quickly our eyes can follow the movement, but our brains struggle to keep up and we get fooled into thinking that both are moving together.
Some of us tried landing a man on the moon, putting a monkey in a tree, putting a fish in a fishbowl, a dog in a kennel, a lion in a cage or a bird in a birdcage.
It is easy to get our eyes to trick our brains!