The Believe hitmaker reveals she was thrilled to be celebrating her milestone birthday back in 1986, when she hit New York for a wild night out with pals.
However, her glee soon turned sour when she received a call from director George Miller the next morning, as she was told leading man Nicholson didn't want her cast as one of his bewitched lovers in the 1987 dark comedy.
When asked what period she would return to if she could time travel, Cher tells U.K. morning show Daybreak, "I would go to the night of my 40th birthday. I was sitting with my friends and we were in a club that we all used to go to in New York and I was thinking 'Wow you know I just dodged age, I just dodged death, I'm 40 years old and I look great and I'm just having a great time'.
"Except in the morning time the man that directed The Witches of Eastwick called me and said, 'You can't be in the movie because Jack Nicholson doesn't think you're sexy.'"
Despite the apparent snub, the singer went on to star in the movie anyway, alongside Easy Rider star Nicholson and fellow screen sirens Susan Sarandon and Michelle Pfeiffer.