Conan O'Brien is late night's silliest, and most apolitical personality. But he slipped into the role of serious journalist Thursday night in Al Franken's first extensive TV interview since he stepped down as a Minnesota senator.

Not that the host of TBS's "Conan" got anything particular newsworthy out of his old friend.

Franken reiterated that he had no other choice but to resign before the Senate could hold hearings looking into sexual misconduct allegations against him.

"My committee work would be at risk, the staff would have been isolated and I couldn't have served the people of Minnesota," Franken said during a somber chat that stretched beyond 13 total minutes, an eternity in late-night TV, especially on a show that's only a half-hour long.

Franken did announce that he would be launching a new radio show on Sirius XM Radio starting this Saturday -- but that tidbit been released earlier in the week.

Perhaps the only comment of note was Franken sharing that he has e-mailed former colleagues during recent televised Senate hearings with suggestions for what they should ask.

Franken also said that since leaving Washington, he had become "a lot more mindful in my interactions with pretty much everybody."

O'Brien may have kept the jokes to a minimum, but he mostly threw up softballs (guests on  late-night TV usually know in advance what questions will pop up). That was no surprise.

Both men are veterans of "Saturday Night Live" and O'Brien has been a longtime political supporter, even hosting a fundraising brunch at his Los Angeles home for Franken in 2013.