The outgoing presenter said that the programme, in which murderer O'Reilly coldly called for his wife's killer to come forward, was his most memorable moment.
Kenny, who will retire from the iconic show tomorrow night, revealed that the O'Reilly interview was the one that stands out from 10 years of Late Late shows.
He said that he remembered "thinking the whole thing was odd" and he claimed that it was O'Reilly's detachment from the situation was the give-away sign of his guilt.
"The body language between Rachel's parents and Joe was cold," he continued.
"You generally get a sense when you're interviewing anyone whether you believe them. It was telling, his lack of emotion. It was not long after Rachel's death, I expected him to be caught up in grief but Joe O'Reilly contained himself."
And when asked by 2FM's Will Leahy about the infamous incident where studio intruder Paul Stokes stormed the set in 2006, Pat said he took it all in his stride. "I presumed it was someone who had a few jars. I wasn't spooked. I didn't suspect a weapon. I wasn't particularly bothered. When you're a broadcaster, there's something in your make-up, the red light bestows calm."
The married dad is also very philosophical about his forthcoming move and said he never knew exactly where his career would take him.
"I enjoy broadcasting. I want to be the best I can be, an accomplished broadcaster. My team has done so well for me. In my 10 years the Late Late Show audiences have never been higher. They're a winning team."
And despite having a tough few years, given the publicity his High Court battle over a land dispute attracted, he said he did not pay attention to the newspapers.
Although he memorably described 2008 as his "annus horribilis", he said that audience ratings were all that really mattered to him.
"I don't think I need to look too much further than the ratings. People vote with remotes."
He'll also be eagerly tuning in to see how his successor Ryan Tubridy handles taking over the popular Friday night show.
"I expect I will watch the new Late Late Show, yes. We'll all be consumed with curiosity. I think Ryan will relish it. I rang Ryan when it was announced and I said my advice was enjoy every week, every month, every year and every decade on the show. If you enjoy it, it will do well and he will do well," he ended.
The veteran broadcaster said that he feels extremely content with his decision to quit the flagship show after 10 years.
"I feel great. I made this decision a long time back but [now] the end is nigh," he said.