Okay but how about the blade of marmora watching the paladins do normal earth stuff like high fives and metaphors and they're just totally so confused. They ask Keith like "why do you ceremonially slap each other in celebration" and he has no idea how to explain it either. Humans are weird.
UMMMM OH MY GOD YES. my other favorite headcanon is that earth is a meme in space. like that earth store in the space mall is the space version of a hot topic and the reason shiro was such a sensation as Champion is half because everyone was just like… oh hey look humans are real after all wow go figure lol