What if a lot of alien species didn’t actually evolve as pack species, and just adapted to living in communities out of necessity? So they can still work and live together, but they don’t have all the little instincts humans have that help them work in a group.
And they are freaked out by us.
We all wear the same clothes. It’s not a uniform— we just somehow all seem to like roughly the same outfits. We fit in so naturally with the people around us that you can use a human’s clothing to tell what country and what time period they are from. Aliens have no idea how we know what clothes are appropriate— they end up having to hire humans to act as fashion consultants after several incidents where diplomats showed up wearing mismatched clothes from various time periods and countries and looking totally ridiculous.
And what about yawning? Aliens who work on human ships say they never fully get used to hearing one human yawn and then having the whole room start yawning along with them. Or telling a joke to one human and seeing humans who say they don’t find the joke that funny cracking up anyway because “their laugh is so infectious!” It’s a common practical joke to tell new nonhuman crew members about this horrible disease humans get, where they feel tired and have an uncontrollable urge to open their mouths. It’s deadly, they say, and very contagious.
New safety procedures have to be worked out for the humans because, on the one hand, you don’t have to go around telling each individual to leave. Humans will just follow the mob. On the other hand, though, you have to be careful not to spread panic, because if one human runs, they all will, and they’ll trample anyone who isn’t fast enough to stay ahead.
Aliens hear humans tell their kids not to give into peer pressure and just get really confused. “Why would they do it if they don’t want to?”
“Because their friends are telling them to do it!”
“But why do it just because they’re telling them to do it?”
“Because they’re their friends!”
“What does that have to do with anything?”
When aliens see earth movies about people being indoctrinated or turned into zombies, it takes them a while to realise that these are horror movies because, from their perspective, that’s just what humans are like.