On this date, Dave Gregg made his major league debut for the Naps, pitching one complete inning. One inning.
Here was his line: six batters faced, two hits, two runs, one HBP, two balks called.
Dave Gregg never appeared in another ML game. One and done! Baseball Reference has a list of 900-plus players who only played in one game for their entire MLB career. Most names are obscure, but one factoid you can use to win some bar bets: Larry Yount. Robin Yount's brother! He was one of the 900+ who only played in one game in the "Show", and never took the field again.