CNN writes, (CNN) - When actor Jack Nicholson stepped on the Oscar stage Sunday night to announce the nominees for best picture, few expected him to toss to a co-presenter. "Tonight, it is my great pleasure to introduce live from the White House, the first lady of the United States: Michelle Obama," he said.Follow @politicalticker Suddenly, the first lady could be seen standing on screen, appearing from the nation's capital in a glamorous silver and black gown. Standing in the background of her cameo, which came about seven minutes before midnight on Eastern Standard Time, was a group of military aides in…