On YouTube Kids, Startling Videos Slip Past Filters

It was a typical night in Staci Burns’s house outside Fort Wayne, Ind. She was cooking dinner while her 3-year-old son, Isaac, watched videos on the YouTube Kids app on an iPad. Suddenly he cried out, “Mommy, the monster scares me!”

When Ms. Burns walked over, Isaac was watching a video featuring crude renderings of the characters from “PAW Patrol,” a Nickelodeon show that is popular among preschoolers, screaming in a car. The vehicle hurtled into a light pole and burst into flames.

The 10-minute clip, “PAW Patrol Babies Pretend to Die Suicide by Annabelle Hypnotized,” was a nightmarish imitation of an animated series in which a boy and a pack of rescue dogs protect their community from troubles like runaway kittens and rock slides. In the video Isaac watched, some characters died and one walked off a roof after being hypnotized by a likeness of a doll possessed by a demon.

“My initial response was anger,” said Ms. Burns, a nurse, who credits the app with helping Isaac to learn colors and letters before other boys his age. “My poor little innocent boy, he’s the sweetest thing, and then there are these horrible, horrible, evil people out there that just get their kicks off of making stuff like this to torment children.”

Parents and children have flocked to Google-owned YouTube Kids since it was introduced in early 2015. The app’s more than 11 million weekly viewers are drawn in by its seemingly infinite supply of clips, including those from popular shows by Disney and Nickelodeon, and the knowledge that the app is supposed to contain only child-friendly content that has been automatically filtered from the main YouTube site.