Robert Downey Jr., star of "Iron Man," posted a tweet Wednesday suggesting that he and his wife, producer Susan Downey, 40, are expecting their second child. "Yo. Susan. Me. Baby. Girl. November. Scorpio?" Downey, 49, tweeted. The couple, who married in Amagansett in August 2005, are the parents of 2-year-old son Exton Elias. Downey's 20-year-old son Indio, from his first marriage, to singer Deborah Falconer, was arrested in Los Angeles on June 29 on cocaine possession charges.