It was staged to promote voting ahead of Tuesday's elections across America - viewers were encouraged to phone in and pledge to vote.
Portman delivered the initiative's most stirring message, reminding her fellow women they weren't able to vote a century ago.
"As citizens, it is our duty to our country, communities, family and most importantly to ourselves to exercise our right to vote," the Oscar winner said. "This is not a right to be taken for granted. Did you know that women in America have been voting for less than 100 years?"
Meanwhile, comedian Chelsea Handler added that Americans have fought and died for the right to vote.
"When that happens we have to look around at our own lives and pay it forward," she said. "We owe those people who fought for us. We owe them with our votes. And if you're a white male who's always had the right to vote, then I hope you vote for all the people who didn't have the right to vote."
Fonda, who joined vote campaigners in Michigan on Tuesday, also had a hardline message for viewers, discussing the importance of personal choices.
"All of these choices create the person that you are," the veteran actress explained. "What we choose to wear just affects a little part of our lives, but elections, and what we choose to do on elections - whether we choose to vote or not - can make an effect on your life for generations to come, so let's do it."