The actress - who plays Ellie Torres in the show, which is created by her husband Bill Lawrence - said Courteney's character is more like the actress in real life than her Friends alter-ego Monica Geller.
She said: "She's goofy and silly in real life, I mean she definitely has a goofy sense of humour and is clumsy and goofy. I think Bill (Lawrence, Cougar Town creator) is writing for her more what she's really like in real life."
Christa went on: "Her character on Friends was so incredibly popular and you see her and think that's the person, when she's not really at all like that."
Christa believes the show, which has been a hit in the States, could last as long as Bill's other creation Scrubs - which she also starred in.
"I read it and don't think it's just doing one pilot - I think it could go for eight years," she said.
She added: "When this script came up I was so happy that Courteney asked me to play her best friend on the show."
:: Cougar Town begins on Living on Tuesday, March 30 at 9pm.