Baseball is an old game, played professionally for well over a hundred years. I don’t usually talk about sports here, in large part because I can’t play them on any kind of competitive scale. However, several have interesting and esoteric rules that developed over time. Here are a couple:

Infield Fly Rule: This rule applies in the following situation: Runners on first and second (possibly third as well), less than two out. If the batter hits a shallow fly or pop-up that should be easily fielded by an infielder, the batter is called out while the ball is still in the air. If this were not the case, the fielder could choose to let the ball drop and make an easy double play. (If the runners led off to try to prevent this, the fielder could catch the ball and still make the double play.) The infield fly rule removes the incentive for fielders to clownishly drop balls and mitigates the risk of getting very easy double plays.

To summarize:

• If the runners don’t lead off, the fielder lets the ball drop. Now the runners are each forced to advance and two can probably be picked off for a double play.
• If the runners lead off, the fielder catches the ball and throws a runner out for a double play.

Dropped Third Strike: If a pitch is the third strike, either because the batter doesn’t swing or swings and misses, but the catcher doesn’t catch it cleanly, the batter is not out but instead entitled to try to run to first. (A “not clean” catch may bounce off the ground first, or may be a bounce off the catcher’s mitt.) The catcher can attempt to either tag the batter out or throw him out at first…

unless there are fewer than two outs and there is a runner on first. As in the infield fly rule, this prevents catchers from intentionally dropping a third strike, then throwing to second and first for a double play before the runners realize what’s going on.

By the way, no matter what happens, this is scored as a strikeout for the pitcher. Scoring could be its own article, if not an entire book.

Ground Rule Double: Many ballparks have a ground rule that if the ball is hit to certain places where it cannot be fielded, it counts as a double for the batter, and all runners advance two bases. For example, a ball lodged in the ivy at Chicago’s Wrigley Field or in the rafters at Minnesota’s Metrodome counts as a double. The most commonly known example is a ball which bounces over the outfield fence, but this is actually not a ground rule at all—this an official rule of baseball, not part of the ground rules for any park.

And for your hyperlinking pleasure:

If you aren’t very familiar with the rules of baseball, Wikipedia is there to help, as always; on the other hand, if this is all old hat to you, there is a neat and difficult quiz you might want to look at.