The tweet, which was attributed to a fake account with Bonet’s name on it, read, "According to the karma of past actions, one's destiny unfolds, even though everyone wants to be so lucky. Nothing stays in the dark 4ever!"
Her rep told People.com, "Lisa Bonet has no social media of any kind. Any posts made in her name were made by impersonators with unverified accounts. She also has no comment on the ongoing story."
The fake Twitter account has since been suspended.
Bonet, who played Cosby's daughter, Denise, on the hugely popular NBC show from 1989 to 1992, is not the only former cast member to be involved in the current sexual allegations against Cosby.
Raven-Symone, who played Cosby's step-granddaughter, Olivia, on the show, denied rumors that she was one of his alleged victims.
She wrote on her Instagram, "I was NOT taking advantage of by Mr. Cosby when I was on the ‘Cosby Show’! I was practically a baby on that show and this is truly a disgusting rumor that I want no part of! Everyone on that show treated me with nothing but kindness. Now keep me out of this!"