Mr. Yuk is a trademarked graphic image, created by the Children's Hospital of Pittsburgh, and widely employed in the United States in labeling of substances that are poisonous if ingested.
In order to help children learn to avoid ingesting poisons, Mr. Yuk was conceived by Dr. Richard Moriarty, a pediatrician and clinical professor of pediatrics at the University of Pittsburgh School of Medicine who founded the Pittsburgh Poison Center and the National Poison Center Network. In Pittsburgh, the skull and crossbones previously used was not terribly helpful, because the Jolly Roger was the mascot for the local baseball team, the Pittsburgh Pirates.
The color was chosen when Moriarty was showing different colors to students, and the green that was chosen was christened "Yucky!" by a young child. Hence, the name and the color. The design for Mr. Yuk was created by Wendy Courtney Brown, then a 4th grade student at Liberty Elementary in Weirton, West Virginia, as part of a Pittsburgh Poison Control design contest.
Over time, the use of Mr. Yuk stickers has gained a certain amount of nationwide usage in the United States. Mr. Yuk stickers usually contain phone numbers of poison control centers that may give guidance if poisoning has occurred or is suspected. Usually, stickers may carry a national toll-free number (1-800-222-1222 in the United States). In some areas, local poison control centers and children's hospitals issue stickers with local numbers, under license. Such an example is in Pittsburgh, where the telephone number for the Poison Control Center is 681-6669.
A memorably scary public service announcement was also produced in the 1970s featuring the theme song, becoming a popular culture icon unto itself for a number of generations.