On Wednesday, the Fox talk-show king will host none other than Jon Stewart, his mirror opposite in very possible way.
It's the Comedy Channel meets Fox in one of the great smack-downs of this television talk era.
Okay, they did meet before in 2004 on Bill O's show, but this time, with President Obama in power, this is going to be very different.
Why did Stewart agree to go on O'Reilly's show?
Because that's where the ratings are, stupid.
And Bill has got them -- four million people a night.
Fresh of his ride around America with that evil mini-me Glenn Beck, O'Reilly seems set to push the boundaries again by having Stewart on.
But that is what is likable about Bill. Even though he is a conservative, he is not afraid to challenge and be challenged.
Really, could you imagine the quicksilver Stewart on Glenn Beck? It would be a wipeout.
But with O'Reilly, it becomes a real heavyweight bout.
Seconds out, round one.