They aired "The Man Trap" first.
Wouldn't that make "The Man Trap" the pilot? Usually the pilot is the first episode.
A pilot is made to sell a series to the network, but doesn't always end up being aired first. See what happened with Firefly
on the Fox network a few years back as an example: network didn't like the pilot Wheedon submitted, so The Train Job
was written and aired first. The actual pilot episode for the series ended up being the last
episode that Fox aired.