"The Cosby Show" star's legacy was left in tatters after dozens of women came forward with allegations of sexual misconduct against the veteran funnyman in the mid-2010s, and in 2018, he was convicted and jailed for drugging and raping Temple University staff member Andrea Constand during an incident back in 2004.
During an appearance on America's "Watch What Happens Live" on Sunday (May 03), O'Donnell admitted she wasn't surprised when the news of his bad behaviour first hit headlines, because Cosby had reportedly upset one of her staff members back when she fronted "The Rosie O'Donnell Show" between 1996 and 2002.
Recalling how Cosby had been recruited to feature as part of her 'Mystery Guest' segment, during which she had to guess who the famous visitor was, O'Donnell admitted she always knew ahead of time who the celebrity surprise would be, so guests had to be coached by her team beforehand.
"In the green room, the producer goes in and she's talking and saying to Bill Cosby, 'You know, she's not going to know that it's you' and he said, 'All she has to do is put her hand right here,' and he put his hand near his penis, (and continued), 'And she'll know it's me.'"
The female staffer was so shocked she broke down in tears, and O'Donnell claims Cosby subsequently had to be lectured about appropriate behaviour by a male producer - although she only found out about the whole incident after the show.
O'Donnell went on to reveal she tried to address the reported incident during her later stint as a co-presenter on "The View", but was repeatedly shut down by producers.
"On 'The View', they would not discuss it," she said. "Every time I tried to bring it up, it became a little fight."
Cosby's representative has yet to respond to O'Donnell's claims, but he repeatedly denied any wrongdoing when previously accused of sexual misconduct.