Christina Aguilera may have opted out of the fourth cycle of "The Voice," but that doesn't mean she won't miss her fellow coaches ... especially
Adam Levine. "When me and Adam are on breaks backstage, you know, we're writing profanity with my red lipstick all over Blake [Shelton]'s trailer while he's napping inside,"
she told E! News. "It's like we have definitely become like brother and sister. We goof around and play around. I'm going to ...