NEW YORK — Parody met its inspiration Thursday when Stephen Colbert and Bill O'Reilly traded guest appearances on each other's shows in an exchange Colbert called "a meeting of the guts."

Colbert has moulded his tough-talking, America-defending persona as host of the satirical "Colbert Report" largely on the Fox News pundit. On his Comedy Central program, Colbert has often spoken reverently of O'Reilly -- or as he affectionately calls him, "Papa Bear."

"The Colbert Report" and "The O'Reilly Factor," the top-rated program in cable news, were taped one after another early Thursday evening, with "The Factor" airing at 8 p.m. ET and "The Report" at 11:30 p.m. ET  (12.30 a.m. ET on CTV).

Once inside Colbert's studio -- decorated for the occasion with a large "Mission Accomplished" banner and a portrait of O'Reilly placed fireside -- O'Reilly seemed to be regretting the decision.

"This was a huge mistake, me coming on here," he muttered.

It may have been a greater error allowing Colbert into the Fox News headquarters, located near the "Colbert Report" studios in Manhattan. There, Colbert smuggled a microwave out of the green room, a bounty which he proudly displayed at the conclusion of his show.

A spokesman for Fox News confirmed Colbert stole the microwave but said it was all in good fun.

Appearing in the "No Spin Zone" of "The O'Reilly Factor," Colbert remained in character -- though it wasn't always easy to tell.

"Who are you? Are you Colbert or Colbert?" prodded O'Reilly, pronouncing the "T" in one case, leaving it silent in the other (as Colbert does on his program).

"Bill, I'm whoever you want me to be," answered the comedian.

O'Reilly interviewed Colbert with a generally bemused attitude.

"Don't you owe me an enormous amount of money?" he wondered.

The interview was followed by a discussion with several analysts on why "The Colbert Report" and its sister fake newscast "The Daily Show" are popular.

Colbert had spent the week preparing for the arrival of "Papa Bear" and hyped it Thursday as "the greatest TV crossover since the Flintstones met the Jetsons."

For the first time, Colbert began the show's interview segment seated, allowing O'Reilly to enter to applause. Well, mostly applause. O'Reilly blamed a handful of boos on "Daily Show" host Jon Stewart, joking he was in the audience.

Colbert's reception included a montage of clips from both shows, titled "Great Minds Think Alike." He also had O'Reilly read several lines for a new O'Reilly-based character in his "Tek Jansen" cartoon series.

O'Reilly also managed one dig of NBC, which he has recently criticized as a liberal-leaning network. When asked what is "destroying America" more -- NBC, activist judges, illegal immigration or gay marriage -- O'Reilly didn't hesitate in answering NBC.

But not all of Colbert's expectations were met. When he prompted O'Reilly to say who would win in a fight between him and his Fox News colleague Sean Hannity, O'Reilly demurred -- and nearly upset the delicate balance of parody and reality.

"Hannity would kick my butt," said O'Reilly.

"I'm effete. I'm not a tough guy."

"This is all an act."

Colbert retorted as though his mirror-image of O'Reilly had been broken.

"If you're an act, then what I am?"

Once the show was over and O'Reilly had left, Colbert turned to the studio audience as he exited the stage and said, finally out of character: "He seems like a nice enough guy."