Popular cartoons are being used to trick young children into watching disturbing content on the internet.
Hundreds of YouTube videos appearing to be episodes of Peppa Pig and Thomas the Tank Engine are actually parodies with inappropriate themes.
According to an investigation by BBC Trending , one video that appears to be an episode of Peppa Pig features a dentist with a huge syringe.
Peppa's teeth get pulled out, and distressed crying can be heard on the soundtrack, reports Mirror Online.
Other spoof episodes feature familiar characters from the Disney film Frozen, the Minions franchise, Doc McStuffins and Thomas the Tank Engine.
While some of the videos use the characters in more innocent ways, others appear to be deliberately designed to trick children into watching disturbing content.
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One channel called "Toys and Funny Kids Surprise Eggs" has a landing page with a picture of a toddler alongside official-looking pictures of Peppa Pig, Thomas the Tank Engine, the Cookie Monster, Mickey and Minnie Mouse and Elsa from Frozen.
However, many of the videos on the channel have titles like "BABY HULK BITES BABY ELSA", "NAKED HULK LOSES HIS PANTS" and "SPIDERBABY CUTS ELSA'S DRESS".
Many of the videos feature graphic toilet humour.
Some of the darker ones also depict violence and frightening situations.
YouTube said that users can flag any problematic content by clicking on the "... More" button underneath a video and clicking "Report".
"Flagged videos are manually reviewed 24/7 and any videos that don't belong in the app are removed within hours," a spokesperson for the company said.
"For parents who want a more restricted experience, we recommend that they turn off the Search feature in the app."
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(Photo: Dave Thompson/PA Wire)
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The company also suggested that parents use the YouTube Kids app , which has a much higher bar for content allowed on the platform.
Parents are able to block specific content, set the age level of videos and report videos.
YouTube also blocks search queries that are vulnerable to returning mature results.
Since the BBC published its report, several of the channels highlighted in the investigation have been removed - including the one containing the video of fake Peppa visiting the dentist.