After 1,129 seasons - or maybe it's 17 seasons, who even knows anymore - of 'Grey's Anatomy', the show has cycled through a number of castmembers through the years.

The new season kicked off with the return of none other than McDreamy, or Patrick Depmsey to his mother, to the show - despite the fact that he died on screen about six seasons ago. We've discussed how it was that he came to back on the show over here, so don't click if you don't want spoilers.

In a lengthy interview with the LA Times, showrunner Krista Vernoff explained how it was that Patrick Dempsey returned to the show after so many years, but also provided an answer as to what happened with Katherine Heigl, who played Dr. Isobel 'Izzie' Stevens, on the show.

While Izzie's storyline was eventually resolved on the show some 10 years after her character's exit, Vernoff revealed that there was a plan in place to do it much sooner. As she tells it, the reason it never came together was Katherine Heigl.

"We had planned to have her come back for an episode to really properly tie up Izzie and Alex," Vernoff told the LA Times. "And I wrote that episode, and it was beautiful. The day before it was supposed to start prepping or shooting, I can’t remember, we got a call that Katie wasn’t coming. Just wasn’t coming. Wasn’t going to do it."

Vernoff went on, adding that she wasn't trying to "bash" Heigl for refusing to appear in the episode. "I don’t know what was happening in her life," Vernoff explained. "I don’t know what led to that decision. All I know is that the night before a thing is supposed to start shooting that is entirely centered on one character and the completion of her story arc, I got a phone call that she wasn’t coming to do it."

However, Katherine Heigl has disputed this version of events, and sources close to Heigl told EW that "Katherine was back in LA after parental leave (when she adopted her daughter) waiting to be called to set." Of course, Izzie's story was resolved just last season, when it tied up Alex Karev's storyline along with hers.

What we do know is that Heigl asked to be released from her contract on the show 18 months early. In 2015, Shonda Rimes - the series creator and then-showrunner - made it clear that Izzie's story was done and that she wasn't interested in having the character back, even to wrap up her story.

Given how Vernoff pretty much placed the blame at Heigl's feet in this most recent comment, the chances of Izzie coming back into the show is deader than Denny Duquette, George O'Malley, or Derek Shepard for that matter.