My BS detector was giving me fits, so I looked this up.
I was under the impression that
Happy Days never had a "pilot" episode. "Love and the Happy Days" (directed by Marc Daniels and Gary Nelson) was actually a pilot for a show titled
New Family in Town, and not
Happy Days. That show concept just later morphed into what became
Happy Days.
If, by "pilot", the question writer simply means the first episode, they're wrong again. Reiner didn't direct that. He just co-wrote it. Mel Ferber directed it.
Once again, my BS-ometer saves the day.