Katie Couric returns to morning television with Good Morning America

Katie Couric returned to morning television for the first time today since 2006, when she left NBC's "Today" show, taking on host duties on ABC's "Good Morning America" for a week.

Couric said, "my heart's beating," on the 7 a.m. show with George Stephanopoulos, filling in for Robin Roberts, according to USA Today.

While at NBC, Couric helped establish one of morning television's longest winning streaks, with "Today" winning ratings every week since 1995, now at 850 consecutive and counting, according to the Associated Press.

The AP said, according to Nielsen ratings, ABC's morning program has been nipping at the heels of "Today," cutting its lead down to only 137,000 viewers last week, the closest since 2008.

Morning shows are still hugely profitable despite declining viewership, said the AP, and none have pulled in as many viewers as "Today."

The media buzz around Couric's week long guest hosting stint has cast the move as a pitched battle between the two morning television programs, with The Washington Post maintaining a live blog of Couric's first GMA appearance. "Katie does a report on precocious puberty. Girls developing breasts as early as age 6. Katie puts on the glasses."

"Today" responded to the buzz surrounding Couric's appearance on GMA by booking "legend" Meredith Vieira to appear on Monday's show and Sarah Palin to co-host Tuesday's show, said The Huffington Post.

More on GlobalPost: Sarah Palin to host NBC's "Today" program

Palin told the Big Journalism website, "I see this as a good opportunity to bring an independent, common-sense conservative perspective to NBC. We’re ‘going rogue’ and infiltrating some turf for a day," according to Politico.

More on GlobalPost: The Argentine economy's fuzzy math problem