Guest Hosts for GMA

With Robin Roberts out getting chemotherapy and a bone marrow transplant, Good Morning America is bringing in all sorts of celebrities to fill in for her while she's gone.

It's a pretty impressive list already.

Among the people who are doing it: Stephen Colbert, the cast of Modern Family (one at a time), Diane Sawyer, Katie Couric, Barbara Walters, and Oprah Winfrey.