Grey's Anatomy fans are buzzing - and in some cases up in arms - over the news the show is planning an episode taking place in an alternate reality, which will feature (among other things) Derek married to Addison.

After all Meredith and Derek have gone through, fans of the show's signature couple aren't exactly thrilled about a new installment revisiting the married Derek and Addison, however it's conceived by Shonda Rhimes.

Is this upcoming episode, reportedly titled "If/Then," a terrible concept designed as a shameless ratings ploy? Or is it a compelling idea, and based on something broader than fans are giving it credit for?

According to TV Guide, Addison and Derek may be the focal point of fan debate, but the triggering "what if" device is more about the impact Ellis Grey (Meredith's mom, played by Kate Burton) would have had.

The worlds of Meredith and of Grey's Anatomy as a whole would have been a whole lot different had Ellis not succumbed to Alzheimer's, and the continued marriage of Derek and Addison is part of that scenario.

This may well be another crazy experiment like the musical episode or the Seattle Grace reality show, but Burton's portrayal of Ellis was always powerful, so there may be something more complex at work.

What do you think? Do you like watching the show take risks in the name of delivering episodes that shake things up, or would you rather stick with conventional Grey's Anatomy? Vote in our survey below:

Grey's Anatomy's alternate-reality episode sounds ...

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.