Sharon Lawrence has Izzie in a tizzy.

This week on ABC's Grey's Anatomy (Thursday, 9 pm/ET), as if cancer-stricken Izzie didn't have enough to contend with, her mother, Robbie, makes tracks from the trailer park to Seattle Grace — and unannounced, at that. NYPD Blue alumna Sharon Lawrence shared a look at her, um, "colorful" guest-starring turn.

TVGuide.com: I want to start off by saying that I for one did not buy you as someone old enough to be Katherine Heigl's mother.
Sharon Lawrence: [Laughs] Well, think about it the way I did when they offered me the role. Like Izzie, she got knocked up when she was 16! Like mother, like daughter — there's absolute legitimacy in that.

TVGuide.com: Plus, Robbie doesn't fancy herself as being old enough either.
Lawrence: Well, no, she's an eternal child down deep ... and right there on the surface too!

TVGuide.com: Is Izzie happy to get this surprise visit from her mom?
Lawrence: No, she has no idea that her mom is even aware of her circumstance, much less is going to be coming to Seattle Grace. That's an interesting thing to examine, that when someone is that ill, it's a challenge to share it with anybody, much less a parent who has not been particularly responsible. I know a lot of folks who have chronic physical conditions, and one of the biggest issues is how it's going to affect the rest of your family, and what it means to manage their emotions.

TVGuide.com: Izzie obviously has her reasons for not wanting her mother to know exactly what's going on.
Lawrence: Because someone like Robbie can be much more of a drain than a support, no matter how well-intentioned. I believe that Robbie with every fiber of her being wants to mother Izzie; the question is whether she's capable of giving the sort of care that someone in Izzie's condition really needs.

TVGuide.com: As the mother-daughter scenes turn serious, was it easy to go there with Heigl?
Lawrence: I tell you, from the first minute that we started working in the rehearsal together, I recognized how open and comfortable she is as an actress. She made it so easy to get to that level of emotional and physical intimacy right away. One of the reasons I've always been attracted to her work is that she just can't fake it, she's so honest. That made my job so easy.

TVGuide.com: There's definitely the feeling that these two have often only tolerated each other. There are a lot of "Oh, my crazy mother" eyerolls from Izzie...
Lawrence: And yet I think they have a similar passion about life. It's not just about tolerating someone in your family that drags you down; there's an effervescence about both of the characters. 

TVGuide.com: It's too bad Robbie didn't surface under better circumstances. Based on her first scene, there could have been an effective triangle with her, Alex and Izzie.
Lawrence: [Laughs] There is right away a sense that Robbie just can't help herself from responding in that flirtatious way. Justin [Chambers] is another one of my favorite actors on the show. He was really charming and sweet to work with. You know, this is actually my first hospital show in all these years! I'm such a fan of [Grey's creator] Shonda [Rhimes] and [executive producer] Betsy [Beers].

TVGuide.com: Might we see more of you as Izzie's cancer story plays out? There's been talk that they want Heigl back for at least a little bit of next season.
Lawrence: The door is certainly open. We really enjoyed the collaboration, and it'd be a pleasure to come back. 

TVGuide.com: What else do you have going on?
Lawrence: I'm producing a music video right now starring Ed Asner, for a great band called The Old Ceremony, based in Chapel Hill, which is where I went to school. It's set in a nursing home and it's about how love never dies. He stars opposite Eileen Ryan, Sean Penn's mother, and it's the sweetest love story. It's really great!