Entertainment Tonight.

Tonight, Conan O'Brien returns as a guest on Late Show with David Letterman for the first time in 13 years, re-visiting his battle with Jay Leno over the Tonight Show.

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"The only consolation I took during that period was that you were happy," O'Brien told Letterman, who went through a similar battle with Leno after Johnny Carson left the Tonight Show in 1992.

Letterman joked that he viewed O'Brien's brief time at the helm of the Tonight Show as "the Golden Age of television."

Watch O'Brien's entire sit-down on the Late Show tonight at 11:35/10:35c on CBS.

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