SNL is bringing in the big guns for the final three shows of its 40th anniversary season: On May 2, Scarlett Johansson will host as Wiz Khalifa makes his SNL debut, no doubt thanks to the Furious 7 hit “See You Again.” Then it’s Reese Witherspoon with Florence + the Machine on May 9, and closing out the season on May 16 is Louis C.K. with musical guest Rihanna. SNL better have her money.