Cuckoo also stars Tyger Drew-Honey as Ken's son Dylan, so Digital Spy caught up with the Outnumbered actor to find out more about the show...
What can you reveal about your character Dylan in Cuckoo?
"My character Dylan in Cuckoo is quite a grungy, moody typical sort of teenager - he's a spiteful younger brother, he's blackmailing his parents, that sort of thing! He's not particularly endearing at first, but over the course of the series - through his love interest and stuff - you see a nicer side to him. He is quite a sweet, sensitive boy.
"I think it's one of those teenage things - he's got an image of moodiness [in his mind] and that occasionally comes through. I think he feels that he ought to be like that because he is a teenage boy."
What attracted you to Cuckoo when you first read the scripts?
"Well, the first time I fully read through the script properly was at the first read-through actually. I was originally drawn to it because in the e-mail from my agent about the audition, it had the premise of the show and I knew that it had both Greg and Andy in it, so that's quite a big deal as well.
"I love the premise and then getting to know my character because he had quite funny lines and quite a few good storylines, so I thought, 'Yeah, they're doing something really good with some great people in it, and I'd love to do it'."
Did you enjoy getting to play a role that's more adult than your Outnumbered character?
"Definitely... to be in something where my character has been directly involved with drugs. I did something recently - a comedy called Threesome - with quite a few of the same crew, which was quite nice because I could just sit there with them and laugh...
"But my character smoked a joint in that and I had this fake weed, so that was quite cool. It is quite exciting getting more sort of sweary, druggy, spiky roles instead of... you know, sitting doing homework, saying 'Mum, I'm going to bed!'."
The relationship between Ken and Cuckoo is central, but how does Dylan interact with the show's title character?
"It's not been the most active relationship. I'd say there's more Greg and Helen [Baxendale]'s relationship which is kind of important, and there's Cuckoo and Greg's, which I think is probably the paramount relationship.
"So I think my relationship with Cuckoo is actually maybe overshadowed sometime, but we definitely do have interactions and there is one point in the series where I have to come out as not gay - it will make sense when you see it! Cuckoo's really proud of me, and by the end it appears that me and Cuckoo are kind of good friends."
Andy is a big comedy star in the US - did he have a different approach to comedy than the rest of you?
"Well, it's all comedy and he is a comedy genius, I'd say, but I think that what you're kind of getting at is the idea that he is from a different calibre. There's American comedy genius and there's British comedy genius, and I think that's part of it - it added to the dynamic of the show."
Outnumbered has obviously been a huge success. Do you think Cuckoo has the potential to be a long-running hit like that?
"I really do. You never really know with a show until you see the edit, because you can make or break something in the edit. While we were filming it, knowing the storylines and the director and how everything was shot, it was clear it was gonna be good - but until you actually see it, you never know how it's gonna feel. Now I've seen it, I'm very happy."
Cuckoo begins on Tuesday (September 25) at 10pm on BBC Three.