On August 29, 1990, Griffey, Sr. signed with the Mariners after being released by the Cincinnati Reds. The Griffeys made history by being the first father and son to play in a game together, but perhaps the most memorable event of their brief time playing together cam on September 14th of that year when Ken Griffey, Jr. and his father Ken Griffey, Sr. became the first and only father-son duo to hit back-to-back home runs in MLB history.
 

Ken Griffey Sr. came to bat in the first inning with a runner on base and no outs. He sent a Kirk McCaskill pitch over the fence in left-center field for his third home run of the season. There to greet him at home plate was the on-deck batter, Ken Griffey Jr.  "That's how it's done, son," Senior said. 

Junior stepped to the plate and hit a ball to almost the exact same spot in left-center at Anaheim Stadium for his 20th homer of the season, and the Griffeys became the first father-son tandem in Major League history to hit back-to-back home runs.

To this day, they are the only father and son to hit a home run in the same game, let alone go back-to-back.

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