Demi Moore, Dwight Yoakam, Oscar-nominated actor-writer Billy Bob Thornton and Gina Gershon are on board to appear in the coming-out episode of “Ellen,” which will air April 30 on ABC to kick off the May sweeps.All four actors, according to sources close to the show, will appear in a dream sequence at a supermarket where Ellen DeGeneres’ character, Ellen, is shopping. In the scene, the supermarket is having sales specials for lesbians, which confounds the confused Ellen. As previously reported, talker Oprah Winfrey, actress Laura Dern and singer k.d. lang are also scheduled to appear on the episode in which Ellen comes out of the closet. Winfrey will play the shrink who helps Ellen discover more about her sexuality than she knew, while Dern plays a love interest.