Have you ever met somebody who didn't seem quite human?

I recently rewatched the video of the woman on the plane screaming that the passenger beside her wasn't human and it got me thinking about something I've seen.

I remember seeing a teenage girl in a small food store I go to address the guy behind the counter as 'human'. "Thanks, human." Stuff like that. I think she was just doing a bit or something but I thought it was strange.