Why Dax Shepard’s co-star Michael Pena passed on ‘Polar Plunge’

When Dax Shepard joined supporters of the Special Olympics’ “Polar Plunge” and dove into Lake Michigan on Sunday, he lucked out to be in Chicago during a mild winter.

“Everyone likes to point that out, to try to diminish my accomplishment — diving into 39-degree water,” the actor and director said with a laugh during a phone interview Monday. “It still felt plenty cold. But it was a great event and very heart-warming to raise money for the Special Olympics.

“Plus it made the rest of the day wonderful! You get that behind you, and the rest of the day is pretty easy!”

As for Chicago native Michael Pena, who co-stars with Shepard in “CHIPS” (opening March 24), there was no way he’d take the plunge. “Not only am I from Chicago and realize how cold Lake Michigan stays — until August! — I also just got finished doing this movie where I was in 40-degree water for 30 minutes. That alone had me shaking for an hour and a half.

“So, just as soon they asked me about doing this, I shot it down. I am donating money to Special Olympics, but no freezing swimming for me!”