Not sure if this has already been mentioned, but humans like to mutilate their bodies with sharp needles and shit and draw weird symbols on them which we call “tattoos”. We also like to pierce our skin and put rings and stuff in them. Why do we do this? Because it looks cool.
I don’t have any tattoos or piercings myself, but from what I hear; it’s very painful. But we do it anyway because we’re tough and we don’t care. Especially those of us who have them all over their bodies.
Could you imagine an alien’s reaction if they saw a human with huge piercings all over their face and weird symbols drawn on every part of their body. It would look something like this: