Jessie Wallace and Shane Richie go days without speaking when they row.
The "EastEnders" actors - who reprise their roles as Kat and Alfie Moon in upcoming spin-off "Redwater" - have a very close bond, but their relationship can be feisty, and Jessie, 45, admits they argue like siblings.
She told Closer magazine: "We just know each other so well, on and off screen. The very first scene we did together was when Alfie came into The Vic and started making all these fancy cocktails at the bar, throwing stuff in the air.
"Then Kat comes in, he smiles at her, and she's like, "Tsk." All the crew were watching on monitors, saying, "These two should be together."
"He makes me laugh all the time, though we're like brother and sister - we'll argue and then not talk to each other for a few days."
And though Shane, 53, admits they argue a lot, they are also very close and he says they have shared a lot of "intimate secrets" with one another.
He said: "We do row, a lot. But most of the time it's because we're so comfortable with each other, it's like the rows you'd have with your best mate.
"We also share some intimate secrets - and we'll take those to our graves."
The pair both had a great time shooting "Redwater" in Ireland.
Shane said: "I loved it. It's been a great opportunity for us and I think fans of Kat and Alfie will love it."
Jessie added: "I just fell in love with the place and the weather while we were filming was great.
"I even went into the sea - but it was freezing. I got brain freeze and couldn't even talk."