Here’s a stat from Gibson’s 1968 season that will blow your mind:
He started 34 games that year, completing 28 of them (with 13 shutouts). In each of the 6 games he did not complete, he was removed for a pinch hitter. He never came out of a game from the mound all season (I think had manager Red Schoendienst tried, Gibson might have killed him).
One I read the other day; in his final appearance in 1975 (he was in the bull pen at that point), Gibson was brought in with the bases loaded. He got the first 2 hitters and then gave up a grand slam to Pete LaCock (son of game show host Peter Marshall). 15 years later in an old timers game in Kansas City, Gibson faced LaCock and drilled him.
I saw him pitch once at Shea Stadium in the early 70s. IIRC, Willie Mays was with the Mets at that point.