Mr. Yuk was introduced in 1971 as a graphic solution to label poisonous substances so that children would know they were potentially harmful. According to the creator of the Poison Control Network, Dr. Richard Moriarity, a new symbol for poison was needed since research showed that children associated the familiar skull and crossbones iconography with adventure and pirates – not death. A line-up of different icons were designed and shown to children under age 5: a mad face, a sick face with the tongue sticking out and a face with Xs for eyes. When asked to organize the faces in the order they liked the best, Mr. Yuk always came in last. Millions of Mr. Yuk stickers were distributed to parents for free to label poisonous substances in their homes. When studies later showed that the stickers were largely ineffective in deterring children from toxic substances (and in some cases kids were actually attracted to items with the Mr. Yuk sticker) the campaign was killed. Still, if you write in to the Pittsburgh Poison Control Center you can get a sheet of Mr. Yuk stickers for free.