[Billy] was under doctor's orders to take a nap every day. The doctor hoped that this would relieve a complaint that Billy had: Every so often, for no apparent reason, Billy Pilgrim would find himself weeping. Nobody had ever caught Billy doing it. Only the doctor knew. It was an extremely quiet thing Billy did, and not very moist. (3.15.1)
And now there was an acrimonious madrigal, with parts sung in all quarters of the car. Nearly everybody, seemingly, had an atrocity story of something Billy Pilgrim had done to him in his sleep. Everybody told Billy Pilgrim to keep the hell away. (4.9.16)
Billy looked inside the latrine. The wailing was coming from in there. The place was crammed with Americans who had taken their pants down. The welcome feast had made them as sick as volcanoes. The buckets were full or had been kicked over.
An American near Billy wailed that he had excreted everything but his brains. Moments later he said, "There they go, there they go." He meant his brains. (5.53-6-7)