Guest stars can be good and guest stars can be not-so-good, but this one sounds like a winner to me. EW's Michael Ausiello has an exclusive report that Florence Henderson will be on Samantha Who?

And if you think Christina Applegate kind of looks like she could be related to Florence, you're not alone. The Brady Bunch veteran has been cast as Samantha Newly's grandmother, Jean Smart's mama. And if that's not blonde goodness and potential hilarity for you, TVGuide.com has another exclusive; Christine Ebersole will play Sammy's aunt. In the very same storyline!