my coworker is a social chameleon and it's so fucking weird

Does anyone know people who seem to completely change depending on who they're talking to?

There's a coworker at my part-time job who's been starting to get on my nerves because of this. When I first met him, he was pretty quiet, so I didn't think much of it. Over time, though, I've noticed that he seems to adapt his entire personality to whoever he's with.

It's not just code-switching or being polite. It's like he studies people, figures out what they're into, and then starts mirroring them. If he's talking to one person, he'll act one way. Then someone else joins the conversation, and suddenly his opinions, humor, interests, and even mannerisms shift to match the new person.

The weirdest part is when we're in a group of three or four people. You can almost see him struggling because he's trying to cater to multiple people at once. Sometimes it feels like he doesn't have a consistent personality underneath it all.