Floyd Mayweather versus Conor McGregor is something a four-year-old would come up with. One of those curious kids who out of nowhere says, “Who wins if Green Lantern fights Wonder Woman?”

That’s what this … fight? … encounter? … scam? … feels like.

Two competitors who have competed in different realms. Who have powers unique to different worlds. Apples and oranges; Marquess of Queenberry Rules vs. Ground Game.

So why is this happening?

Because we are rubes. Marks. Ripe for the plucking.

The fight may gross something north of $600 million, from on-site (in Las Vegas) ticket sales and $99 pay-per-view TV buys.

The rest of us can’t fault the contestants for going forward with this competitive scandal.

Mayweather could be in line for a $250 million payday; McGregor, for $75 million — or about $65 million more than he has been paid in his UFC career, where management abuses fighters even more than they abuse each other.

The root of this is that we apparently are so bored that the “who wins if a boxer fights a martial artist?” trope has eaten the brains of all sort of people, including a lot who know better.

This should not be close. Mayweather has never lost a boxing match. McGregor has never competed in one.

It is impossible to take this seriously. McGregor cannot use any of his MMA tricks. He can’t go to the ground; he can’t jump atop a fallen opponent and beat him senseless. He has to out-Mayweather Mayweather even as he finds out what boxing is really about.

This isn’t the first time boxers have been lured into fighting athletes from different combat sports. The most noted of these uniformly ridiculous encounters pitted Muhammad Ali against wrestler Antonio Inoki of Japan in 1976 with a set of rules that has never quite been interpreted.

It turned out to be one of the biggest jokes in sports history, with Ali on his feet trying to punch at Inoki while the latter spent most of 15 spectacularly dull rounds on his back, kicking Ali behind the knee, trying to bring him down so he could grapple. Here, have a look.

It was ruled a draw. It is remembered as a farce.

If McGregor had insisted on some sort of hybrid match, he might have a chance. But going into the ring with unbeaten Floyd Mayweather, 49-0, and playing by his rules …

No chance.

Yet, this is happening, spurred along by months of “Acting 101” verbal violence from the combatants. It really has felt like a carnival event. “Step right up!”

Mayweather is 40 and doesn’t have much punching power left, but unless his skills have atrophied enormously over the two years since he competed … he should hit McGregor, a lot, and rarely be hit by a guy who has never competed as a stand-up fighter.

The chances of this being competitive are close to nil. Some people who consider themselves experts in a “sport” no one has seen suggest McGregor may not land a stiff punch no matter how long the fight lasts.

Wake me when it’s over.

No, change that. Don’t wake me.