"Other kids' games are such a bore!
They gotta have rules and they gotta keep score!
Calvinball is better by far!
It's never the same! It's always bizarre!
What can you do if you can’t win in the arena of ideas? Well, if you’re on the Dems’ team you…
Change the Senate filibuster rules, pack the Supreme Court, allow propagandized children to vote, get rid of the Electoral College and, most recently, change the requirement that whistleblowers have firsthand knowledge of an event they blow the whistle on. It’s like political Calvinball, named after Calvin of Calvin and Hobbes, who has no patience for games with rules:.
Calvinball has no rules; the players make up their own rules as they go along, making it so that no Calvinball game is like another. Rules cannot be used twice (except for the rule that rules cannot be used twice).
TV Tropes explains a bit more thoroughly.
Calvinball is a game which we see characters play but whose rules we don't know. This allows authors to create games that are absurdly silly, complicated, or arcane.
It's particularly useful to show crazy or destructive characters wreaking mayhem in what looks to the audience like organized chaos…
It also explains other games previously popularized by Dems before Calvinball was invented:
…if the basic rules are described to the audience in any way, or if the game already exists in Real Life and audiences can look it up, then it's not Calvinball. You may instead be dealing with The Points Mean Nothing (where the game is explained but the scoring is arbitrary); Moving the Goalposts (where the game is explained but characters try to change the rules to their own advantage); Gretzky Has the Ball (where the sport is real but the characters play it like Calvinball); Artistic License – Sports (where the sport is real but just inaccurately portrayed); Screw the Rules, I Have Plot! (where the fictional game is technically defined but inconsistently portrayed); or Gameplay Roulette (where the rules are defined, but the game itself unpredictably changes them on the players).
When a sport doesn't exist in real life, but has defined rules that can be followed, it's a Fictional Sport.
Now do you understand?