Conan O'Brien at the Primetime Emmy Awards on September 20, 2009 in L.A. Credit: Dan MacMedan/WireImage

Conan O'Brien found out the hard way that physical comedy is harder than it looks.

The Tonight Show host, 46, reportedly suffered a concussion after hitting his head while filming a stunt for the show on Friday with Desperate Housewives actress Teri Hatcher.

The bit involving Hatcher, whose episode was canceled and replaced with a rerun, poked fun at her recent participation in a triathlon.

"We did this bit and at the very end, when we ran in to cross the finish line, he slipped as he was crossing the finish line and hit his head," Hatcher tells Entertainment Tonight of O'Brien's accident.

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"He didn't get off floor right a way, but then he [seemed] like he recovered and [pulled] it together, and they did an instant replay, and you could really see his head hit the floor," the actress said. "He did go to hospital and he does have a concussion."

The NBC network confirmed O'Brien was taken to a local hospital for observation, but did not elaborate on his current condition.

In a statement, O'Brien, who took over the late-night staple from Jay Leno in June, used his trademark humor to reflect on the incident.

"Last thing I remember I was enjoying the play with Mrs. Lincoln, and the next thing I knew I was in bed being served cookies and juice" O'Brien said in the statement.

There is no word yet from NBC about plans for future Tonight Show episodes.