What conditions are necessary for an infield fly rule call?

An infield fly is a "fair fly ball ... which can be caught by an infielder with ordinary effort, when first and second, or first, second, and third bases are occupied, before there are two outs." It doesn't necessarily need to stay in the infield, but don't tell that to Braves fans.

And why does the infield fly rule exist?

If there was no infield fly rule, infielders would purposely drop the ball to turn double or triple plays. That might speed up the game, but it'd be sort of cheap, right?

How many strikeouts are possible in one inning?

A dropped third strike allows a runner to claim a base, so technically, there's no limit to the number of strikeouts in an inning.

The rules expressly prevent baseball players from spitting...where?

Rejoice, baseball players: You can spit anywhere except for on the ball. That would make it a spitball, which would be a violation of Rule 6.02(c)(6). Of course, you might want to avoid spitting on the umpire—they don't appreciate that.

How many spare balls must an umpire have at any given time?

Rule 4.01 states that the umpire must keep two alternate balls in his possession at all times. You can carry more if you'd like.

A pitcher takes two minutes to deliver a pitch. Can the umpire penalize the pitcher?

Rule 8.04: "When the bases are unoccupied, the pitcher shall deliver the ball to the batter within 12 seconds after he receives the ball. Each time the pitcher delays the game by violating this rule, the umpire shall call 'Ball.'" If you've ever sat through a Pedro Baez relief appearance, you know that this rule isn't actually enforced, but it is on the books.

A ball gets stuck in a player's glove, so he throws the entire glove over to another fielder to record an out. Is that legal?

It's perfectly legal, and it happens. Cubs pitcher Jon Lester has thrown his glove to first baseman Anthony Rizzo on two separate occasions. He successfully recorded both outs.

A fielder takes his hat off and uses it to catch a batted ball. What happens?

This wasn't always the case, but in the modern game, Rule 7.05(b-e) provides the penalty if a fielder intentionally touches a ball with a part of their uniform that is "detached from the proper place on his person."

A runner at second is hit by a fair ball, and there's no infield fly call. What happens?

Per rule 7.08(f), the runner is out, provided that it's a fair batted ball and there's no infield fly call. However, a runner isn't out if the ball touches a fielder first.

An outfielder accidentally deflects a fair ball into the stands. What happens?

Per rule 6.09(h), it's a home run. This has actually happened multiple times, but the most famous probably occurred on May 26, 1993, when Carlos Martinez hit a long fly that bounced off of Jose Canseco's head and into the stands.

Which of these is not something that an umpire can do?

MLB officials can eject umpires, but umpires can't eject eachother, unfortunately. Apart from that, umpires can eject anyone in the ball park, although they usually restrict their ejections to the players on the field. That's not always the case—in 2012, an umpire at a minor league Daytona Cubs game ejected the park's deejay for playing a clip of "Three Blind Mice."

A pitcher injures his arm during an at-bat, and asks if he can throw with his other arm. Can he?

Oddly enough, pitchers are allowed to switch arms in case of an injury, thanks to rule 8.01(f). However, they don't get to warm up with their new pitching arm. This rule helps to prevent switch pitchers from switching arms in the middle of an at-bat.

A batter makes contact with the catcher's glove while swinging at a pitch. What happens?

This would be catcher interference, and while it's rarely called, the rules state that the batter gets first base. With that said, the batter's manager can decline the interference call (which would make sense if the batter gets a clean hit on the play).

A pitcher delivers his pitch...and the ball gets stuck in the catcher's mask. What happens?

Per rule 5.09(g), runners advance one base. This rule rarely comes into play (for obvious reasons).

According to the official rulebook, what player can be in foul territory when a pitch is delivered?

Rule 4.03: "When the ball is put in play at the start of, or during a game, all fielders other than the catcher shall be on fair territory." There's no real reason for any player to be in foul territory, other than the catcher—and if the pitcher is in foul territory while delivering a pitch, something has gone horribly wrong.

A pitch is delivered while the catcher is outside of the catcher's box. What happens?

Per 5.02(a), it's officially a balk. You rarely see catchers balk, but...well, their job is pretty simple. And painful.

A batter hits a home run with men on base. A baserunner gets injured and can't run the bases. What happens?

Rule 5.10 states that the manager can substitute a pinch runner. That came into play on Sept. 14, 2005, when Tony Graffanino hit a homerun for the Boston Red Sox with Gabe Kapler on first. Kapler ruptured his Achilles, and after a five minute delay, the Red Sox substituted Alejandro Machado for Kapler. If Graffanino had passed the injured Kapler, Kapler would have been out, and his run wouldn't have scored. Fortunately, Graffanino knew the rules.

There are two outs. A runner tries to steal home, and the pitch hits him. What happens?

According to the rulebook, the run would score if there were less than two outs...but since there are two outs, the out is recorded first, and the run doesn't score. It's complicated, but that's baseball for you.

A batter hits out of turn (the manager delivered the wrong lineup card), but the umpire doesn't notice for several batters. What happens?

This happened most recently in May of 2018; the New York Mets turned in the wrong lineup card while facing the Cincinnati Reds. When the umpires noticed the error, they made the correct call—the current batter was out, and play resumed with the lineup in the correct order.

A runner standing on second base decides to steal first base to create a distraction while the runner on third steals home. Is this legal?

It's not legal, but it used to be. The practice was outlawed in 1908. However, in the modern era, at least one player has stolen first from second—but not for a tactical reason. In a 2013 game against the Chicago Cubs, the Milwaukee Brewers' Jean Segura got hung up trying to steal third. Thinking quickly, the Brewers' Ryan Braun moved up to second, but was called out. Segura, confused, headed toward the dugout...then to first base. The umpires allowed Segura to claim the base. Segura later tried to steal second for the second time in the same inning. This time, he was thrown out.

A spectator leans over the outfield fence and catches a ball a player was going for. What happens?

While spectator interference calls are generally at the umpire's discretion, Rule 6.01(e) states that "if spectator interference clearly prevents a fielder from catching a fly ball, the umpire shall declare the batter out."

A batter hits a line drive that hits one of the umpires. What happens?

As Rule 6.01(d) explains, the umpires, bat boys, attendants, and pretty much every other non-player on the field are considered part of the park. As long as they're not interfering intentionally, the ball remains live.

This might be the most difficult question in all of sports: When is a balk a balk?

The balk rules are covered in Rule 6.02, and there are quite a few of them, but the simplest description of a balk is when "the pitcher, while touching his plate, makes any motion naturally associated with his pitch and fails to make such delivery."

What happens if a pitcher makes an illegal pitch without runners on base?

If there aren't runners on base, it's not actually a balk—it's just an illegal pitch, and therefore a ball, according to rule 6.02(b).

Can a pitcher wear a Band-Aid on his non-pitching hand?

A comment to Rule 6.02(c)(7) specifically states that a pitcher can't have a bandage on either hand. Sorry, pitchers.

A pitcher intentionally throws at a batter's head. What's the penalty?

It's an automatic ejection and suspension. As the rulebook states, "To pitch at a batter’s head is unsportsmanlike and highly dangerous. It should be—and is—condemned by everybody."

A fielder gets into an argument with a fan and calls them a name. Per the rulebook, what happens?

This falls under section 6.04, "Unsportsmanlike Conduct." Of course, players frequently interact with fans in...colorful ways, so most umpires ignore this rule.

A manager is ejected, then sneaks into the stands wearing a fake moustache. What happens?

When you're kicked out of a game, you're not allowed to come back. That didn't stop New York Mets manager Bobby Valentine. On June 9, 1999, he was kicked out of a game for ordering a call. He returned to the dugout (not the stands, unfortunately) with a fake moustache. He was fined $5,000 for the transgression. "I regret it," he said later. "It's going to cost me a lot of money. I don't regret the fact that it lightened the team." The Mets won the game with a 14th inning walkoff.

Assuming one team is ahead, when is a game officially a regulation game?

Per Rule 7.01, a game is officially a regulation game after five innings, provided that one team is ahead.

Can a triple play occur if the batting team doesn't put a ball in play?

Not only can it happen, it did happen on Sept. 2, 2006. The Tampa Bay Rays were playing the Seattle Mariners. Seattle's J.P. Howell struck out, and the ball was dead. Catcher Dioner Davarro threw out Adrian Beltre, who was trying to steal second. Jose Lopez tried to steal home, but was thrown out at the plate. That's a triple play without a hit—a pretty incredible feat."