... L.Q. "Sonny" Clemonds points at Data and asks Riker, "What is that?" Then Data turns around to see what he's pointing at.
Data must look particularly artificial in person, more so than on the TV screen. There must be something about him that screams "artificial" to an individual from a more technologically advanced society. When he was stuck in the 19th century, no one seemed to think Data was not a human, just that he was particularly pale. Clemonds, though, immediately picks up on Data being something other than human. I wonder if 24th century individuals would initially have an even stronger reaction to Data than Clemonds did.