I've written about this once before (I won't link to it, because why?), but only in passing, and it deserves more than that.
Entering the 1966 season, the newly-moved-to-Atlanta Braves' Tony Cloninger was a promising young pitcher. He was 26. He'd been in the league for five years, and had seen a steady increase in just about everything -- innings, wins, strikeouts and strikeout rate, ERA+ (with the corresponding drop in ERA), etc. In '65, Cloninger finished in the top ten in wins, innings, strikeouts, starts, and homers per nine (while also leading the league in walks, and posting just a 107 ERA+). He wasn't a superstar, yet, but he seemed to be heading in the right direction.
One thing it didn't look like he'd ever become, though, was a hitter. Cloninger was a pretty typical pitcher on that front; he'd finally hit his first home run in 1965, and in his five-year career, he was a .174/.179/.211 hitter in 329 plate appearances. That's a little bit better than the pitcher's norm -- NL pitchers hit .138/.170/.175 as a group in '65 -- but certainly not enough better to get excited about.
Then, 1966 happened.
OK, it's not like Cloninger suddenly learned how to hit. Through his first 15 starts, he was hitting .121/.147/.152, and the pitching wasn't going well, either. But then suddenly on June 16, Cloninger threw a mostly-gem against the Mets, allowing a run on five hits and three walks with four strikeouts, and oh by the way went three-for-five with two homers and five RBI. After a second inning strikeout, he hit a three-run homer in the third, then added a harmless single in the fourth and a two-run shot in the fifth, helping the Braves to a 17-1 win. The five RBI tied, at the time, an all-time National League record for pitchers.
Fast-forward about 2 1/2 weeks, to July 3. Here's a great contemporary account, from the Reading Eagle:
San Francisco, July 3 -- pitcher Tony Cloninger is in a class all by himself today after becoming the first National League player to hit two grand slams in one game as the Atlanta Braves buried the league-leading San Francisco Giants, 17-3.Two grand slams. 410 feet. Opposite field. That's some real power there. And: nine RBI. Quite a day.
Cloninger, who also knocked in a run with a single, set a one-game record for major league pitchers with nine runs batted in.
Cloninger made his own job easier as he won his sixth game in his last seven starts and brought his record to 9-7.
Cloninger's first slam came off a 3-2 pitch by reliever Bob Priddy in the first inning and capped a seven-run outburst. It cleared the center field fence near the 410-foot sign.
It was almost the same spot that Atlanta's Joe Torre had drilled a three-run shot only moments earlier.
Cloninger's second came in the fourth inning -- also with two out -- off an 0-1 pitch from [Ray] Sadecki and it was an opposite-field shot to right.
Cloninger also became the second National League pitcher to hit two homers in a game twice in one season. The first was Don Newcombe, of the Brooklyn Dodgers in 1955.
To this day, only thirteen other players have ever hit two grand slams in a game (list here), and as you might guess, none of the others are pitchers. Just Cloninger. In fact, it's never been done by a center fielder...but it's been done by a pitcher. (Another weird quirk about that list: only once, by Nomah in 1999, has the feat been accomplished at the accomplisher's home park.)
Among pitchers, unsurprisingly, Cloninger's 9 RBI is still a single-game record. He no longer also shares the second-place spot in National League history; Robert Person had seven (with two homers) for the Phillies against the Expos in 2002. And a few more guys have had six RBI, including the Astros' Dave Giusti later in the same year as Cloninger's feats, and he did it without the benefit of a home run: on August 21, 1966, he had two bases-loaded, bases-clearing doubles while throwing a complete-game shutout in the Astrodome. Cloninger is now one of only three NL pitchers ever to have two multi-homer games in a season; Rick Wise did it in 1971 (and one of them came during a no-hitter).
The pitching star thing never quite happened for Cloninger, now 71, who has been a MLB pitching coach and was still, as of 2010, consulting for the Red Sox. After those five promising seasons, he took a big step back in '66, with a 4.12 ERA (89 ERA+) in 257 innings. He'd never throw 200 innings again, and his one remaining season of a better-than-average ERA came with the NL-champion Reds in 1970 (9-7, 3.83 in 148 innings). He was out of the league for good after 26 bad relief innings the following year, aged 31.
He didn't suddenly emerge as a hitter, either: he hit one more home run in '66 (later in July), though he did bat .232 the rest of the way, and hit just six more in his post-'66 big league career, batting .193/.212/.297 (41 OPS+). But for those two days in less than a month, Cloninger was pretty incredible.