I believe that the leisurely pace of baseball gives it the perfect comedic timing. Football or boxing with its quick pace is more in line with the action movie; in boxing though there is more of a dramatic flair. Because baseball reflects a more realistic and endless stream of time, it seems that there is time enough to tell jokes. With baseball's pace thoughts do not always have to focus on the intensity of competition, but also, "cutting loose."
One prime case is the classic Simpson's episode, "Homer at the Bat" which pokes fun at baseball while embracing it. The episode works within the culture of baseball from the quirks of Mr. Burns' baseball signs to more nostalgic references taken from "The Natural" to the use of signing the biggest names in the sport for tactical advantage. It eventually culminates in Homer's at bat. One where eight out of nine players go missing for various wacky reasons and he has to bat for (now) former Met slugger Daryl Strawberry. It's Homer's final do-or-die, as the game's now in his hands after being benched for superstars.
There is real life basis for this kind of characterization as some of baseball's personalities have been known to have a goofy sense of humor. Four-time Cy Young Award winner Greg Maddux was known to wipe his snot on other players as a joke. Kent Hrbek, according to ESPN's Tim Kurkjian, would go camping and played tape recordings of his "best" farts. This doesn't just happen to individuals, but between organizations, such is the case when the independent Northern League traded one of their own players for sixty cases of beer.
There are plenty of angles at work in the National Pastime as I've mentioned earlier: nostalgia and hope. But there is also the laughter that bridges the gap between innings and is a component that give baseball its unique identity. As famed Cubs announcer Harry Caray once said, "I'll tell you what's helped me my entire life. I look at baseball as a game. It's something where people can go out, enjoy and have fun. Nothing more."