I'm going to play a gross but harmless prank on a kid
What do you think he'll do?
He will get angry and will pretend it's a joke, but deep down inside he will get upset.
You can have fun with kids. But don't have fun at their expense, that's cruel.
Of course, but it's not so much fun when they are into the joke.
While it might seem fun to play with kids until they get upset, it is mean. They have strong emotions and those emotions are valid even though they are kids.