This Is The Most Dangerous Children's Toy Ever Made

Summary
Mark and Ethan try out B'loonies, a brand of bubble making toys from Fischbach's childhood that was discontinued due to its toxic fumes and the potential for harmful chemicals to build up inside the straw, making it dangerous to inhale. After shaping their balloon animals, Mark ignites the two figures to see how flammable the chemicals are, which causes them to catch fire and burst immediately, singeing the end of Fischbach's hair.