Not fair to any man
You see, this is a problem with twins; they are always on the look out to joke on unsuspecting victims. Imagine that this poor guy fell for it, grabbed up the twin sister, and planted a huge kiss on her? Their little plan would have backfired in a heartbeat, and the real twin girlfriend would have been livid. Lucky for this guy, he was able to keep his hands to himself when the other twin came out, and that kept him out of the basement with his girlfriend.