Izzy and her partner Gary are still eager to become parents, but when their adoption plans fail at the first hurdle due to Gary's criminal record, Katy shocks the pair by announcing that she'll be their surrogate.
Katy's idea will divide the extended Armstrong-Windass clan, leading to fireworks at baby Joseph's christening this Friday. In the face of disapproval, will Katy go ahead with her plan?
Digital Spy recently chatted to Georgia May Foote, who plays Katy, to hear more about the storyline.
What was your reaction when you heard that there would possibly be another baby in Katy's future?
"I just thought, 'Oh no, another body suit!' (Laughs) No, I knew it would be a really good storyline and great to sink my teeth into. I couldn't wait to get the scripts to start reading more about it."
Have you known the story was coming for a while?
"Well, we don't really get told very much until we get the scripts. We might hear a couple of things floating around in the green room, but we don't find out for sure what's going to happen until we get the scripts - which we then film two weeks later. So everyone was asking me what was going to happen, and I didn't really know myself!"
Why does Katy make the surrogacy offer to Izzy? Has she really thought it through?
"I don't think she's necessarily thought it through as much as she could have done. It's quite a spur of the moment thing, but in her mind, she just wants to repay Izzy for everything she did for her when she was younger. Izzy brought Katy up, so now she wants to help her out in return. So that's the main thing that's running through her mind."
How does Izzy react to Katy's suggestion?
"At first, she thinks it's a stupid idea. Izzy doesn't understand why Katy wants to do it, especially as she's just had a baby herself and she's still so young.
"In the end, Katy manages to twist her arm slightly. Katy, Izzy and Gary then go to see the doctor just before Joseph's christening. It's just a quick chat at that point, rather than anything serious. Izzy goes along just to keep Izzy and Gary quiet, really. But after the meeting, Izzy starts to come round to it a little bit more…"
Is Gary more keen on the idea than Izzy is?
"Yeah, he is at first. I think that's because Izzy never thought she would have a baby, so she'd already got her head around the possibility that she'd only ever be an auntie. When she had a miscarriage recently, she knew that she couldn't do that to herself again.
"But Gary still hasn't come down from that cloud - he's doing everything to stay up there and make sure that they do have a baby. It's just driving him mad - it's all he wants to do."
Chesney has no idea that Katy, Izzy and Gary have gone to the appointment. Why doesn't Katy consult him?
"I don't think she necessarily does it on purpose. She just becomes so wrapped up in everything, and it all happens so quickly. Katy gets Gary and Izzy interested in the idea, then they go to the doctors, and afterwards they have to dash off to the christening. Chesney then finds out at the church, which wasn't planned! Katy hasn't ignored Chesney on purpose - she was going to tell him."
Why does the truth come out at the christening?
"It's because Owen wants to know why Gary, Izzy and Katy were late arriving at the church. He doesn't believe them when they say they were just running late, and he keeps pestering them about it. Gary eventually blurts out that they were at the doctors, but Owen is confused because he wants to know why Katy was there.
"Obviously Owen is being very overprotective and he won't let it drop. In the end, Gary explodes and reveals why they were really at the doctors. Owen thinks Katy being a surrogate is an absolutely stupid idea, and then it all kicks off! Owen just can't see the logic in what they're planning."
Do the arguments ruin the christening, or does everyone pull together for Joseph's sake?
"It does ruin the christening, and everyone ends up going their separate ways! There are arguments between Katy and Chesney, too. They're both also angry with Owen for making a scene at the christening. Nobody's happy with anybody really, and it'll take quite a lot to get them all back together."
Will Katy take Owen's disapproval into account?
"No, I don't think she will. In her head, Katy thinks it's the right thing to do for Izzy. She doesn't understand why everyone's being so horrible about it - she just wants to help her sister out. She hopes that she can make Owen understand why she wants to do it."
Will Chesney come round to the idea?
"Yeah, he does in the end. At first, he's very mad at Katy for not telling him, but he does eventually say that he'll stand by Katy if it's what she wants. He still makes it clear that he's not over the moon about it, though!"
After two years at Corrie, how are you finding your time at the show?
"It's absolutely flown by. Time flies by when you're having fun, and I'm definitely having fun. Maybe the next two years will fly by as well. We'll just have to see - I might end up like Bill Roache!"
How long did it take to settle in on the show?
"I think I had a bit of an advantage, because a few months before I started as Katy, I'd been there for a couple of days as a different character. I kind of got the nerves out of the way then!
"I'd say maybe a year down the line was when I really felt like I'd found my feet and got to know everybody. So this last year has been really good and really comfortable - I've really enjoyed myself."
Whatever happens with the surrogacy idea, is it going to be a busy time ahead for the Armstrong-Windass clan?
"Yeah, we've had a really busy couple of months. I think I'm going to be quiet again now just for a little bit, but then by the end of this year I'll be quite busy again. So there'll be a little break - just so we're not on the screen all the time - but I think we are going to be quite a busy family. I've heard some good things from the bosses, so we'll just have to wait and see."
Are you all quite close when the cameras stop rolling?
"Definitely. I get on really well with Debbie Rush, who plays Anna. We always go for dinner together as a big family as well. We practically take up the canteen now as the family is so big! We all really get on, and the banter we have off set kind of follows us onto the set as well."
Do you think Katy and Chesney have a long-term future as a couple?
"I hope so. I think it's nice to have a couple on the street who aren't having affairs or murdering each other! They're not too lovey-dovey but they are quite a friendly couple, so it's a nice balance."
Who would you like Katy to have more scenes with?
"I've always wanted to do more in The Rovers, even though those scenes take a long time to film! Now that Katy is 18, I've actually started having quite a few Rovers scenes which is really exciting - especially working with Sue Johnston now that she's joined the show.
"I recently had a scene with Sue where I was quite snappy towards her character Gloria, so afterwards I apologised to her! It was my first scene with her so I didn't want to offend her!"
What are your hobbies outside of work? Is there anything about you that would surprise Corrie fans?
"There's nothing too surprising - I like shopping, going to the cinema, and spending nights in with a DVD and a takeaway. I enjoy seeing a lot of my family, as I'm quite a family girl. People may be surprised that I can play the French horn but I can't read music - so I don't know how I do it!"
Finally, what would you be doing if you weren't an actress?
"Because I've acted since I was young, I've always had jobs in between, so I've worked in a pub and stuff like that. Before joining Corrie, I was actually going to university to do criminal psychology, because I did really well in that at college. So if I wasn't an actress, I'd probably still be studying to do that!"
> Read the latest 'Coronation Street' spoilers and news
Coronation Street airs Mondays, Thursdays and Fridays on ITV1.