In an unprecedented move, this is the second week in a row that the Nob Nation star will appear on the chat show. He will finally break his silence about what happened between him and the GAA star in Kehoe's pub on October 19.
Last week saw him on the show - but it wasn't to be interviewed. Instead, he did a skit impersonating all seven presidential candidates before ending with an impression of Eamon Dunphy - where he asked Galvin for an apology.
However, he was met with a mixed reaction from viewers of the show and has been spurred into giving his own account of what happened.
"He rang producers last Wednesday and asked if there was any way he could go on the show. Ollie said he wanted to set a few things straight and basically explain what went on with him and Paul Galvin," said a show insider.
"Initially, they weren't keen on the idea. They would never have the same personality on the show two weeks running. But he was quite emphatic in saying that he wanted to put his side of the story across to viewers. He got a load of reaction from his appearance on the show last week - both negative and positive. This is his chance to clear the air."
On the night in question, it was alleged that Galvin verbally abused the comedian and acted in an aggressive manner towards him. The bust-up was spurred on by a previous skit by Callan where he alluded to the sports star's friendship with Grainne Seoige and his fashion sense.
Also appearing on the popular show will be broadcaster Ray D'Arcy and weather girl Evelyn Cusack.
Last week's show had a record audience of 491,000, despite being up against X Factor on TV3.