It's called the "NeeDoh challenge," where kids put a gel-filled toy called a "NeeDoh" in the microwave, which can cause it to explode.
"It's really bad, it's dangerous. Don't do it," said 11-year-old toy customer Bryce O'Rilley.
O'Rilley and his 13-year-old brother know a lot about squishy toys, including the TikTok trend involving the little collector's items.
The challenge is leaving many kids badly burned.
It happened to a 9-year-old near Chicago. Now, the fire marshal in Nassau County says two young girls from Floral Park, ages 4 and 8, were also burned on Thursday.
"It exploded and oozed it's gel on on them," said Nassau County Fire Marshal Chief Michael Uttaro. "The 4-year-old suffered burns to her legs, I believe her arms, and a little bit of her face."
Authorities are pleading with parents to be aware.
At Sugar Crazy toy store in Plainview, where these types of toys fly off the shelves, the manager also tries to make sure consumers are educated, especially about not leaving them in hot cars either.
"If you're keeping it in an enclosed location for a period of time, yes, they could explode and burn," said Dani Liberman, the manager of Sugar Crazy Toy Store.
But they are popular for many other reasons.
"Cause I have ADHD, so it's easier for me in school. I focus better if I am doing something with my hands," said toy store customer Chase O'Rilley.
He told Eyewitness News that he has 38 NeeDohs, and 47 other squishies.
"They sell out from about 15 to 30 minutes," Liberman said. "If we post about it, people will start lining up in the store."
Fire marshals are reminding people that trends do come and go, but injuries can be permanent.
"I think that's terrible that the kids get burned with it. I think they should play with them responsibly," said Holbrook parent Ally Loodus.
For any kids searching for the trend, TikTok is now putting up a screen, warning customers, as well.
As for the two little girls from Floral Park, they were taken to Nassau University Medical Center's burn unit, where they were in serious condition.
The fire marshal's concern is that if this happens again, the next time could be far worse.
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