Elon Musk has responded to Johnny Depp's accusation that he had an affair with Amber Heard during their marriage and is challenging the actor to a "cage fight."The Tesla founder said in an interview with The New York Times that he "definitely was not having an affair with Amber while she was married to Johnny." He called the accusation "totally false." Musk also refuted a scandalous claim that he had a threesome with Heard and Cara Delevigne."We did not have the threesome, you know.