(Kaiba is about to jump off a castle's battlement)Serious Business is when a story revolves around an activity where a sizable portion of the in-story population takes it far more seriously than they should. If the popularity of some mundane object rivals that of Elvis Presley, The Beatles, and Michael Jackson combined, or if there are mainstream schools devoted to it instead of teaching reading, writing, and arithmetic, then it's Serious Business. It's often a Silly Reason for War, and can turn a casual conversation into a heated Cavemen vs. Astronauts Debate. Frequently "opposed" by the Cavalier Competitor. Compare “Stop Having Fun” Guys. In musicals it's often demonstrated that Dancing Is Serious Business. For the saying that "The Internet Is Serious Business", see GIFT. Related I'm Not Here to Make Friends. Compare Duels Decide Everything, Comical Overreacting. When a relatively minor crime is treated as Serious Business, that's Felony Misdemeanor. Contrast Not a Game, Matter of Life and Death.
Yami Yugi: Dude, don't you think you're overreacting a little? I mean, it's just a card game.
Kaiba: Card games are serious business!