Madness string 3439

Random mermaid
Things done in the name of research... Walking the Underworld, taking pictures. Mixing drinks, testing recipes. Wandering through the lists, wandering through the fields. Starting a game in one world, ending it in another still. Place everyone in a room and just see what they do. Let's get out of here.

Based on the name and this situation, I assume a piss disk is when you pee into a shallow saucer, freeze it and then slide the frozen disk under a door so that it melts later and forms a pool of urine in someone's apartment.