The third season of Catastrophe is due to begin in the UK in late February.
The final episode includes ‘emotionally powerful scenes’, which were among the last she ever shot.
Fisher suffered a medical emergency during a transatlantic flight from London to Los Angeles, following a book tour.
Writer / star Sharon Horgan explained Fisher’s schedule meant “We didn’t have her for very long”, adding: “We wanted to know her better.”
“For series three we wrote a bigger part for her character and we got to spend a lot more time with her. She was funny all the time. She was an incredibly witty person and liked saying arseholey things to everyone but also a really kind, lovely, supportive person.
“Even the second series we didn’t have her for very long,” Horgan continued. ‘She flew over and did her bit for a day or two and of course we wanted to get to know her better, we idolised her, But we didn’t really have a chance.
“Then in series three we wrote this bigger, chunkier part for her in episode 6 and got to spend time with her and she became part of the gang. We feel very privileged and honoured.”
Horgan and Rob Delaney have yet to work out how to address her death in the comedy, in a fourth season.
“It’s hard to know think about what to do,” Horgan said at a press screening. “Hopefully, time will pass and we’ll have a fitting finish to that story.”