That was John Drew Barrymore, a member of the famous Barrymore acting family, and father of Drew Barrymore. He died a few years ago.
After his Star Trek goofup, the Screen Actors Guild suspended him for six months, and he was unable to find similar work. The details are in Solow & Justman's Inside Star Trek: The Real Story
. He survived it all, but I don't recall him ever being that popular in those days.