Talk show host Rosie O'Donnell will join the new Broadway musical Seussical as the Cat in the Hat for four weeks beginning Jan. 16. O'Donnell — who made the announcement on her show Wednesday — will sub for vacationing Cat David Shiner. "Rosie wanted to do the role," Lynn Ahrens, who co-wrote the Dr. Seuss-inspired musical, told The Associated Press. "She obviously can't do eight shows a week or commit to a year. We adore her, and she loves the show. It's the kind of role a personality can come into and do for a short time." Broadway's No. 1 fan — last seen on the Great White Way as Betty Rizzo in Grease — will do six performances a week, while Shiner's understudy, Bryan Batt, will portray the Cat during the Saturday and Sunday matinees. O'Donnell will donate her salary to charity.