One player hitting three home runs in one game is rightly seen as an impressive accomplishment. Reggie Jackson hitting three home runs in Game Six of the 1977 World Series is one of the most replayed moments in Yankees' history.
On May 15, 1923, Wally Schang "accomplished" a feat that is arguably more amazing than hitting three home runs in a game. It's not more amazing in terms of player performance. Schang didn't have the biggest hand in his performance at the plate that day. I mean in turns of pure amazement, what happened to him that day is arguably more ridiculous than if he had hit three home runs.
In May 1923, the Yankees were in the midst of a season that would end in their first ever World Series win. Getting the majority of the starting time at catcher that season was Wally Schang. Schang was a very good hitting catcher. Before 1921, when the Yankees acquired him, Schang had a career 131 OPS+ in eight major league seasons with the Athletics and Red Sox.
Schang's 1923 season was the second worst season of his career (excluding the final two years of his career, where he only played a combined 75 games.) Coming into May 15th, he was hitting just .205/.303/.218.
The Yankees were playing the Tigers that day. Detroit's starting pitcher on May 15th was former Yankee Rip Collins, who played for the Yanks from 1920-21. The 1921 season was Schang's first season with the team. The Yankees won their first pennant that season, losing the World Series in eight games to the Giants (it was a best-of-nine series for a few years).
So on May 15th, the Yankees beat the Tigers 9-5. After Herb Pennock got chased from the game early, Carl Mays pitched 6.2 shutout innings. Meanwhile, the Yankee offense put up six runs against their former teammate, with Babe Ruth driving home three.
Schang made five plate appearances that day. One of them came against Tigers' reliever Ole Olson. The other four were all against Collins. In three of those plate appearances, Collins hit Schang with a pitch.
No other Yankee was hit with a pitch that day, just Schang. If there is any particular reason if Collins did that on purpose, it cannot be found online. That can't be ruled out, though. He issued just two walks, so it's not as if Collins was particularly wild that day. There's a definite possibility that Collins didn't like Schang and decided to take it out on him by hitting him three times. Although Schang faced Collins four times that day--if you've hit him three times, you might as well do it all four.
The odds are that Schang was just extremely unlucky. While no one has been hit more that three times in a game, Schang is one of 23 who are tied for the all-time record. Getting hit three times is rare but not unprecedented. It very well just might have been that three pitches got away from Collins and they all happened to be against Schang. That's probably more likely, but way less fun. Schang's on base percentage did go up 16 points that day, so there's that.
If ever a time machine is invented, I would love to go find out what the deal with Wally Schang and Rip Collins was.
All data courtesy of the Baseball-Reference Play Index