Planking was just lying down on things, so hardly an instance of teenagers endangering themselves.

The tide pod thing wasn't exactly what it seemed to be. Some children with learning disabilities and some people with dementia had died from mistaking laundry pods for food. At some point, some media outlets decided to sensationalise it by leaving out the bit about learning disabilities. That meant that there were teenagers who thought other teenagers had died from eating them, so they could make videos pretending they'd done that, just like teenagers have staged videos to make it look like they're doing dangerous things that they aren't really doing ever since people have let them have cameras. Some of them decided that the easiest way to pretend was to put a real laundry pod in their mouth, pretend to chew it and swallow, pretend to die, and then cut the video and spit it out. If they checked the relevant warnings on the packet, they just said not to eat them and to rinse their eyes if they got any there, so this plan might seem safe. However, laundry pods are so corrosive against mucous membranes that putting one in your mouth and spitting it out immediately because it starts to burn immediately can still be fatal or cause permanent injury. The media reported the deaths and injuries as if teenagers were intentionally eating laundry pods, rather than pretending in a way the packet implied might be safe, so most people weren't learning that pretending was also deadly and that the warnings on the packet weren't exhaustive, so it just made fake tide pod challenge videos even more tempting. If the reporting had been more responsible, then most people would have first heard even pretending to eat laundry pods can kill rather than teenagers are eating laundry pods.