07/15/2010 at 12:00 AM EDT
may be back to work
on the set of Grey's Anatomy
, but according to the actress, it hasn't been a super-happy homecoming.
"Our first day back was Wednesday and it was -- I'm going to keep saying this because I hope it embarrasses them -- a 17-hour day," Heigl told David Letterman
during a visit to the Late Show
on Monday, "which I think is cruel and mean."
One reason for her lack of pep: her good pal T.R. Knight
's departure from the show
"It was actually kind of really great to be back," she said. "All my friends are there and at this point, they're sort of like family, but it was a little weird because T.R.'s not there anymore."
As open as she is about her feelings about the show, Heigl remained tight-lipped about the fate of her character, who was last seen in an ambiguous scene
after undergoing surgery for a brain tumor. "You last saw Izzie, you know, flatlining," she told Letterman. "So, I won't give it away but, you know, I'm there so I'm either there as a ghost, on the other side or I survived a disease no one survives."
"I'm guessing if you're working 17 hours, that means you're not dead," Letterman observed.
Heigl's reply: "What if, however, Dave, I was in a bed in a coma for 17 hours, they could do that to me."
Despite the long days shooting the medical drama, Heigl said she hopes Grey's Anatomy
, which returns to ABC on Sept. 24, will stick around for a while.
"We have another two years, I think, at least in the contract," she said. "Hopefully the show goes, you know, ER
time, which would be cool." -- Brian OrloffTell us: What state will Katherine's character Izzie be in when the show returns?