What does the Financial Control Board for New York City have in common with a comedy club?

Louis C.K. was there.

The comedian made an unannounced visit Tuesday afternoon to a mundane meeting of the panel, which was set up in 1975 to oversee municipal finances as the city teetered then on the verge of bankruptcy.

During the meeting in midtown, Louis C.K. -- real name Louis Szekely, 47 -- sat next to Amy Spitalnick, a budget spokeswoman for Mayor Bill de Blasio, and jotted down notes on paper. He said nothing before leaving.

Reached by email, another de Blasio spokeswoman, Ishanee Parikh, would say only, "Louis C.K. is shadowing the mayor for a project in development."

Later in the afternoon, the comedian spent hours behind closed doors with de Blasio and his team at City Hall.

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The pair emerged hours later to a frenzy of reporters and photographers.

Why is a comedian trailing a mayor? one asked.

De Blasio: "There's a lot of comedy at City Hall."

Louis C.K.: "It's a total coincidence. I just happen to be going to all the same places as him."

In March, the comedian also played the mayor's "anger translator" during the annual Inner Circle dinner, helping de Blasio respond to skits by the city's political reporters.