Given their combative history, it should come as no surprise that O’Donnell would want to help S.N.L. pile on to its increasingly confrontational portrayal of the president and his close circle. When news circulated late Monday night that Trump’s biggest issue with S.N.L.’s Spicer sketch was McCarthy’s gender, someone floated the idea that perhaps his old nemesis, Rosie O’Donnell, should play Trump’s top advisor: Steve Bannon. And as that idea picked up steam on Twitter, it made its way to O’Donnell herself, who was immediately game.