Mariah Carey is famous for going all out on her Halloween costumes, and now she’s built an extra closet at home for outfits for her twins, Moroccan Scott and Monroe. Carey’s husband, Nick Cannon, told pals at Chateau Garden’s opening at the Paris Hotel in Las Vegas on Saturday that she’s “so excited” about dressing the kids for their first Halloween, she needed extra storage in their New York apartment. He added, “She’s been dressing them up and sending me tons of pictures. It’s like they’re prepping for a tour!” Carey will give the first public glimpse of her twin boy and girl, now nearly six months old, on ABC’s “20/20” Friday during an interview with Barbara Walters.