Read on to find out what they had to say about Rachel's dads, where they see Rachel and Kurt in five years' time, and why Lea doesn't want Barbra Streisand to have a cameo on the show...
Glee creator Ryan Murphy hinted recently that we might get to see Rachel's dads in the future...
Lea: "I hope so! I just keep my fingers crossed. I've been begging him and asking him for so long, 'When is that going to happen?' and he keeps saying, 'I don't know, I don't know'. So I know just as much as you do, but I would love that, of course. I think it's so important. I think the fans and the audience love when you get to see the characters' home lives and that's something I really hope we do more of in season three. Like, what are Brittany's parents like? Or what are Mercedes's like? What's her family? Does she have brothers and sisters? And so Rachel's as well."
Do you have any dream casting for Rachel's dads?
Lea: "When I think about who they are, I have two people in my mind. I really do think that one of Rachel's dads is Nathan Lane. I know that's sort of stereotypical, but in my mind I envision him as one of them, for sure."
What about the other one?
Lea: "The other one is a director friend of ours. I don't know if he can act. If he could it would be him. I'm still casting in my mind the second dad but Nathan Lane, I think, would be perfect."
What do you see your characters doing in five years once they've graduated from college?
Lea: "Okay, so..."
Chris: "Go, go! We do this every day. Go!"
Lea: "I definitely think they should go to college in a big city, I think like NYU. I can see Rachel going to like the [musical theatre training] CAP21 programme and studying like intense theatre. She's smart, she is very smart. She does very well at school. I got into NYU, so she definitely could get in! I don't know how that happened. Then I definitely think that they would get a teeny tiny studio apartment, probably the size of this room, and go on like open calls and look through Backstage magazine to try and find auditions."
Chris: "Oh my God! That's actually really funny."
Lea: "And then go on auditions. Kurt would probably work at the department store."
Chris: "For sure. Or he'd have an internship at Vogue."
Lea: "Yes! And Rachel would probably teach little girls ballet or something like that on the side."
Chris: "On one hand I hope it is because I think kids need to see a relationship like that - a positive relationship like that - because there really isn't one their age. I'd love there to be an example for them to look up to. But then again I don't want it to be fake because relationships that age never really last. So I hope that it's realistic but I do hope that it lasts."
Do you think attitudes in high schools are shifting as a result of Glee?
Chris: "I certainly hope so. I'm not in high school anymore so I don't know, but I've heard from fans and letters that have said, 'This happened, but now Glee's on, it's this now'. Many, many heartwrenching stories from fans and people out in the country. I don't know - I surround myself with positivity towards the issues so I don't know. I've been told yes, but I certainly hope so."
One of the interesting things about the season finale was Rachel thinking about her career versus her relationship with Finn. How do you think that will play out in season three?
Lea: "I think she's pretty staunch on what she wants to do and where she's going. I don't think she's going to change her mind and I think the question will be whether or not he joins her. I think that's going to be the big season three surprise."
Do you feel under pressure to up the ante in season three and do bigger numbers?
Chris: "Now that you mention it, I guess so!"
Lea: "I guess so! Yeah, I mean, of course. This year they're taking on a few more new writers, so I think that will allow more people to write for more characters. I love doing the big numbers. I love doing the theme episodes. One of my favourite things from this past season was when we took an album - we did Rumours by Fleetwood Mac. I think that would be a really awesome thing to do again. But my main thing that I would love to see as a fan of Glee, like I said, is to really get into the character and who they are and what they do outside of school. I think that that's interesting. And then of course the themed stuff and the album episodes are all really cool too."
So what would be your dream song to perform on Glee?
Chris: "I've done all mine. I'm out! I'm good, I'm good."
Lea: "I'm done!"
So do you have input into what songs you get to sing on Glee?
Lea: "We've done a lot of events where I've sung songs, and if ever Ryan Murphy was there he'd be like, 'That was really nice', and I'd be like, 'Okay, great. Are you going to let me do it on the show now?' That's how I got 'My Man', which was my number one song that I wanted to sing on Glee. I did it at an event, I sang it for Barbra Streisand, and he was there as well. I'd been begging and begging and begging him and then he saw me do it at the event, and I said, 'Now can I do it?' and he said yes."
Chris: "I just blackmail and bribe."
Lea: "I audition!"
Is Barbra Streisand the one big guest star you'd love to have on Glee?
Lea: "No, I don't [want her to come on]. Idols should be kept as idols. Not that I think she would ever disappoint me - I'm sure if she came she would blow me away and be everything that I've ever imagined. But I think that keeping idols as idols is important. And I don't think that everybody needs to be on Glee! I definitely think that there are people that fit the bill of what it means to be on the show. She obviously is one of them, but you'd have to write the storyline that Rachel has gone mute for a week which we all know is not possible! You'd just have to wheel me in and wheel me out! So that would just be weird and I don't think that that would work."
Chris, you recently said you want Princesses Beatrice and Eugenie in Glee - is that right?
Chris: "No, I never said that! I mean, I'm sure that'd be great, but no, I never actually said that. That was completely false, that statement. But I met them and I was over the moon that I actually met some people that were royal. It was great. I would love Kate Middleton to be in Glee. Wouldn't that be fantastic? That would be great."
Can you imagine a number for Kate?
Chris: "All she'd have to do would be just stand there. That's it. That's all she needs to do. I think I've just decided that Kurt loves Kate Middleton. I love Kate Middleton, so Kurt loves Kate Middleton."
Lea: "There you go! That's how Barbra Streisand happened. Lea loved Barbra, then Rachel loved her. It's going to happen for you, I know it!"
Chris: "Kurt's Barbra is Kate Middleton!"
Lea: "That's perfect!"
Lea: "I think everyone has a little something in them that is their character, and everyone has something that is completely different from their character. I think Ryan Murphy is so great at being attentive to who we are as people and bleeding that into our characters and our storylines, but at the end of the day we are actors."
Chris: "I think everyone is more like their characters than they're willing to admit!"
Well, Ryan built up the character of Kurt after he saw you, didn't he, Chris? You originally auditioned for Artie.
Chris: "When I auditioned for Artie, when I read the lines, it was nothing like Kurt is now. Absolutely not - it was completely different. My original contracts still say 'Artie Two' on them because they didn't have the character written. So they decided they were missing the voice of the gay character and they gave it to me and they just let me go with it, thankfully. I never got any, like, 'Oh no, Kurt's more like this, Kurt's like this', they just kind of let me do what I wanted."
Lea: "Ryan wrote Rachel Berry with me in mind, so... I really don't have anything to say about that!"
Chris: "Seeing you in the first audition and being - 'That's her. Rachel Berry'."
Do you have Rachel's naughty side, Lea? Would you ever send someone to a crack house?
Lea: [laughs] "No! Definitely, definitely not!"
Do you like playing that naughty side, then?
Lea: "Love it. I love it. I love when she does things out of being crazy. Of course, she builds it in her mind like, 'I have to do this, this is right, this makes sense, this is the best thing for everybody' and then does it and is completely crazy. And then I like her having to do the thought process of stepping in and going, 'That probably wasn't right, that was wrong', and then it all ends in tears."
So what's the secret of Glee's success?
Lea: "Chris Colfer."
Chris: "Thank you, I was going to say the same thing! I think there are so many things for people to relate to - there's either a character or a situation that people can identify with and then we add music to that. Music is a universal language and when you add that to the mix - I mean, it's unstoppable."
Lea: "... Ditto!"
Glee returns for its third season on September 20 on Fox in the US and on September 22 on Sky1 in the UK.