Sharon Horgan thinks she has a "weird alchemy" with her 'Catastrophe' co-star Rob Delaney.
The 47-year-old actress and Rob, 41, also write the hit Channel 4 sitcom, and she believes they share a creative spark that's "hard to put your finger on".
Sharon explained: "I think there's a weird alchemy there - something that's hard to put your finger on.
"I think sometimes Rob doesn't know how funny he is until I burst out laughing and write it down. Then when I read it back, he bursts out laughing. It's pretty bonkers."
Sharon and Rob are currently in the process of writing the new series of the show, which concerns their characters' dysfunctional relationship.
And the Irish star has admitted that the creative duo concluded the previous series of the sitcom without knowing where exactly they intended to take the plot.
Speaking to the Independent newspaper, Sharon said: "We're writing it at the moment and we film in July.
"I think we always end the previous series with a big question mark that we don't know the answer to. Then you spend a few days together and start figuring it out. We spend a lot of time working on our outlines to figure out where the series is going. It's the rewriting that you figure a lot of the more difficult stuff out."
The most-recent series ended with Rob's character on the verge of failing a breathalyzer test following a car accident.
But Sharon has promised that the new episodes will be noticeably "lighter".
She explained: "I guess [the darkness] is intentional in that we decide we're going to talk about alcoholism or deal with depression and illness in the family. I know we're not picking the lightest of subjects but we're certainly not deciding we have to go dark.
"In a weird way, this latest series feels pretty light at the moment - and I think that's because we don't want to get lost in the drama of it.
"We do want to talk about stuff that people respond to because I generally feel people like seeing issues they have in their own lives reflected on screen, and when it's done through comedy, it feels even better.
"But at the same time, we're really aware it's a comedy show and we want to make sure it's really funny so at the moment, it's feeling lighter than the other series. But we'll see what happens in the rewrite."