Further defending the gift, he exclaimed, "It was joke! Take a dump on the stage, load him up, get him back!"
O'Brien has apparently changed his mind about the horse since his "warm letter."
"From what people are talking about, Conan will just not shut up about the horse. The horse has gone crazy, maybe its from being around Conan all day," Letterman quipped. "Of course he's unridable, all he had to do was take a dump on the stage."