WASHINGTON — For Senator Al Franken, the political became personal at a “Saturday Night Live” cast party, of all places.

It was there in New York two years ago that Mr. Franken, a Minnesota Democrat, ran into Lorne Michaels, the creator of the NBC show and his former boss when he was a writer and performer there. Mr. Michaels was chatting with Brian L. Roberts, the chief executive of Comcast, which had recently acquired NBCUniversal in a deal that Mr. Franken opposed.

“I fought to prevent this!” Mr. Franken blurted out to the two men.

It was a potentially awkward moment that Mr. Franken defused with the kind of blustery humor that delighted audiences during his years as an entertainer. “We all had a laugh, fun was had by all, and I went on,” he said in an interview.

But for Mr. Franken, antitrust issues involving big companies are no joking matter. The man who created such famous “Saturday Night Live” characters as the self-help guru Stuart Smalley is now a serious policy wonk and a self-made expert in antitrust matters like price-fixing and monopolization.