The 'Star Wars' legend - who died in December 2016 - had a guest role as Mia Norris, the mother of Rob Norris for the first three seasons of the comedy series but the 42-year-old actor and his co-creator Sharon Horgan don't believe she even read a script before signing up for the programme.
Speaking at a Times Talk event, he said: ''Our theory with Carrie . . . we believe firmly -- this isn't a joke -- that she agreed to do the show just because it shot in London.
''We don't think she watched the pilot or read the script . . . She literally learned what the show was well after it had already aired.''
Sharon previously revealed she and Rob had written a special tribute to Carrie in the final episode of 'Catastrophe', which will come to an end after the end of the current fourth series.
She said: ''It's the last episode we're ever going to do, and I can tell you that it's a little bit of a tribute to Carrie Fisher.
''I can tell you that we really wanted to mess with everyone's heads. It's emotional, and it's a little bit longer than usual.
''All of Rob's family are there, and it's not in England. That's enough, right?''
Sharon and Rob had confirmed the show was coming to an end before the start of series four and she admitted they felt it was the right time to bow out while people were still enjoying the programme.
She said: ''We've been doing it for a long time - from the start of it to now it's probably six years - doing a show that we absolutely love, and getting to a point where we thought, 'Well, what if we can't think of something that's original and funny anymore?'
''I would say writing episode four was maybe the hardest one in terms of coming up with stuff that felt original or new or like we had something new to say. So I think we just felt like, maybe, quit while we're ahead.''
'Devour You' is a fantastic follow up to Starcrawler's debut album and represents a move on in terms of sound and, in part, direction.
Salvation Jayne's third birthday bash was a riot of colour and a celebration of a band very much enjoying what they do.
We're feeling the nostalgia this month.
American Thighs was released on this day in 1994.
Gloo is a new supergroup consisting of UK mystic-beat producers Iglooghost and Kai Whiston as well as nu-pop singer/producer BABii.
Listen to her new single Forgive Me now.
His new album Underneath It All is out now.