Unlikely pals Mel Gibson and Britney Spears are solidifying their friendship with a joint vacation to Mel's house in Costa Rica. According to E! News, the pop star, who was befriended by Mel and his wife, Robyn, when she was going through her very public troubles, arrived with Mel, Robyn, her father, Jamie, and some youngsters at 3:18 p.m. in Costa Rica yesterday on a private jet. They'll be staying at Mel's property in the Barrigona province of Guanacaste "for a couple of days," an insider tells E! News.