He appeared via a video link and when presenter Charlie Stayt asked where he was, Moloney used the word “s***hole”.
"I'm at home, this is our farm here that we're doing up, this is the place that we call Chateau S***hole actually, because we are going to pull it all apart and build it up into another nice shiny new farm,” said the actor, who made his name as Ramsay Street’s Toadie Rebecchi.
Stayt didn’t appear to clock the slip-up and pressed on with a remark about Neighbours coming back.
But viewers noticed it and thought it was hilarious.
"Highlight of my week was seeing Toadie off Neighbours saying ‘chateau s***hole’ on BBC Breakfast just now," one person posted on Twitter.
Another commented: "Toadie off of @neighbours just said chateau s***hole on BBC Breakfast and nobody noticed."
"Toadie swearing on BBC Breakfast wasn’t how I anticipated this day starting, but it was delightful," joked another.
Somebody else tweeted: "Hahaha, Ryan Moloney ‘Toadie’ from Neighbours saying s***hole on BBC Breakfast just now. And no one in production clocking it."
"Toadie just got away with saying ‘Chateau S***hole’ on #BBCBreakfast and I don't think they realised he said it as we didn't get the usual apology from the presenter for the bad language," said another viewer.
Then this week it was suddenly announced that it was returning to TV with a new series that will be available on Amazon Freevee in 2023.
A BBC spokesperson said: “We apologise for the language at the end of the show and for any offence caused.”
Watch: Neighbours cast announce Amazon revival