09/22/2012 01:10 pm ET

'The Voice': Christina Aguilera Opens Up About Bond With Adam Levine

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 miss it."

Usher and Shakira will replace Aguilera and Cee Lo Green when "The Voice's" fourth cycle begins in 2013, but Aguilera has expressed interest in returning to the NBC singing competition.

Meanwhile, the Maroon 5 frontman has another project on his plate: His role on "American Horror Story: Asylum," which he admits freaks him out.

"I'm still too scared to watch it," Levine said. "But I'm gonna try and beat my fear of really creepy, scary things like that by doing it. I think that's a good way to tackle that fear."

"The Voice" airs on Mondays and Tuesdays at 8 p.m. ET on NBC.

"American Horror Story"