U-No-Poo is a product of Weasleys' Wizard Wheezes that causes constipation in the unknowing taker. The pills can be mashed up and mixed with food or drink. The product was advertised in the main window of the shop in the summer of 1996 in yellow writing and on a purple background. Mrs Weasley was less than impressed with the slogan, fearing that her sons would be "murdered in their beds" for making fun of the Dark Lord. Ron, however, found the name to be "Brilliant".
Harry Potter once noticed that it seemed as if his classmates had overdosed on U-No-Poo as they practised trying to cast spells without saying an incantation, as they were purple in the face and straining as they tried to make magic without speaking.