(Serious question, read description) How normal is it that girls jokingly slap each other's butts?

Let's keep some thing in mind: First, no, im not trying to sound like a creep; Second, i know it's nothing sexual, it's just a joke.

So, what happens is that i quite often see girls jokingly slapping other girls butts, so what im asking is how normal is it that girls do that, because i like creating fictional characters and stories (im not a professional or anything), and i'd like to know if you girls find it normal enough for it to be a gesture within fictional characters. I guess i'd like to hear specially from the girls who are in friend groups who has this joke.

(Serious question, read description) How normal is it that girls jokingly slap each other's butts?
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