Love this, being on Ellen's show is a BFD.  
Have been hoping this might happen ever since GPN's White Rabbit was used for Anne Hathaway's entrance on her show last month.   
http://ellen.warnerbros.com/2010/03/anne_hathaway_surprises_the_audience_0306.php
Ellen has a huge following, is a bfd herself and certainly seems to have total control of her show and who is on it.  She's always made it clear she loves music and has had many breaking and established artists as guests.  I can easily imagine her loving the band and getting a huge kick out of Grace's quick wit and free spirited personality. 

Wally, I'm thinking it would be hard for someone as well known as Ellen Degeneres to just pick up and go to a regular show the way we can . . but hey, ya never know. :D