The Upright Citizens Brigade’s 15th annual Del Close Marathon, which wrapped up another weekend of around-the-clock improvised comedy, attracts thousands of comedians and comedy fans from around the world and offers surprises of all sorts. Performers you wouldn’t expect to see on a show but do — Michael Cera acted in a scene with Amy Poehler improvising her lines in the scene; Samm Levine hamming it up as part of the annual time-warped Match Game ’76 tribute (photographed above by Meghan R. Ross); Louis C.K. providing the monologue inspirations for the marathon’s final performance of ASSSSCAT. And performers you know you’ll see but doing very unexpected things.

Shannon O’Neill, a UCB veteran and regular with both The Stepfathers and ASSSSCAT, approached me at 2:29 a.m. Sunday near the office door of the UCB’s Chelsea theatre. “Sean, you’ve got to do my show!” O’Neill said as she made her way to the stage for “THE VINE Show, 150 scenes in 15 minutes.”

Did I take her suggestion and heighten it at the top of my intelligence? Did I commit to the #DCM15 theme of commitment, as suggested Friday by Poehler and then referenced by O’Neill?

As O’Neill wrote on her Twitter @spotastic on Sunday afternoon: “Last night was fun. I love photos and short vid clips, lets keep anything longer than 6 sec. off the net. It was for those there. #DCM15

You just had to be there.

So for those who were and those who weren’t, please enjoy reliving — or experiencing vicariously for the very first time — over and over again in six-second bursts, the improvised controlled chaos that is, was and will once again be the Del Close Marathon.

FRIDAY

Actually, that’s Don Fanelli with Chris Gethard during The Stepfathers reunion show: