A knock-down, drag-out fight between the two principal morning talk shows began this morning (Monday) with Katie Couric returning to the air on ABC's Good Morning America at the same time of day that she did when she co-hosted NBC's Today show. Couric, who will be filling in for Robin Roberts this week, acknowledged that she was "a bit nervous" as she joined what for her was once The Enemy camp, doing mostly celebrity interviews and confiding to co-host George Stephanopoulos, "I'm riding shotgun. I'm a little rusty." With Couric, ABC is hoping to come out ahead in the ratings war against rival NBC for the first full week since 1995. (It beat Today on two mornings in October 2007.) Her return received high praise from Washington Post TV writer Lisa de Moraes, who commented, "Katie's back where she belongs." Meanwhile, ABC is waging a counterattack by teaser. It promised that an unnamed "legend" would appear on this morning's show, touching off a spate of rumors on entertainment-related websites about who the legend would turn out to be. Among those mentioned Oprah Winfrey, Will Ferrell in his Anchorman Ron Burgundy guise, and former host Bryant Gumbel. Gawker.com even reported that J. Fred Muggs, the chimp who appeared on Today with Dave Garroway in the 1950s, was being brought out of retirement, but that the appearance had been canceled "due to legal reasons." (The report appeared on Sunday, which was April Fool's Day.) The legend turned out to be Meredith Vieira, who replaced Couric on Today when Couric left to anchor the CBS Evening News in 2006. NBC has also announced that Sarah Palin, who had a disastrous interview with Couric when she was the GOP candidate for vice president in 2008, will be co-hosting Today on Tuesday. And finally, the network teased, Ryan Seacrest will be appearing on Tuesday's edition of the morning show to "make a big NBC announcement." Today's New York Times said that Seacrest will likely announce a deal with NBC to make "occasional contributions" to Today several weeks out of the year and will have a role on NBC's coverage of the London Olympics this year.