He was known for being a pioneering black umpire, his longtime weight problems, and his controversial home plate umpiring in Game 5 of the 1997 National League Championship Series—when his generous strike zone helped the Florida Marlins' Liván Hernández strike out 15 Atlanta Braves batters.

He was the home plate umpire for two no-hitters (Terry Mulholland in 1990[2] and Ramón Martínez in 1995) and worked third base for Tom Browning's perfect game on September 16, 1988.

Richie Phillips, executive director of the umpires' union, felt that Major League Baseball might reconsider its stance in contract negotiations rather than doling out millions of dollars in severance pay.

Aside from his girth, he was also well known for his jocular personality and wide smile, which had a disarming effect on game participants who took issue with his calls.

Gregg's son Kevin has worked with numerous sports teams in the public relations department, and currently serves with the Philadelphia Phillies as Vice President of Baseball Communications.

Son Eric Joseito was well known as a lacrosse coach before becoming an account executive at Dell EMC in the Philadelphia area.

Gregg mentioned in his autobiography that umpires who usually work night games were prone to watch network television dramas; a photo of him with Eileen Davidson is in the book.