Also, with the newer Treks, the toilets weren't something they were going to focus on just because it can get too juvenile. As far as bathroom references go, the episode of DS9 with the Bajoran sail ships featured a scene with Jake Sisko commenting on the toilet which had been designed for zero g, I remember one episode of Voyager where power was rationed, the crew was mostly confined to the mess hall, and Neelix was asking Janeway about the logistics of having to share three toilets for the entire crew (something she hadn't considered.) Finally one episode of Enterprise featured the crew doing a teleconference where they were answering questions that had been sent by school children and one of the children asked them what happened to the waste.