NBC announced Thursday that the longtime "Nightline" anchor joins Harry Smith and Meredith Vieira as correspondents on "Rock Center." Since leaving ABC News in 2005, Koppel has done work for the Discovery Channel and NPR.
The newsmagazine debuts Halloween night at 10 p.m. ET.
Williams says his goal is to make "Rock Center" the "Cooperstown of our craft. Ted is a consensus Hall of Famer."