Don't listen, kids.
Due to the decay of the freeonic/platonium transduction coils (used in refrigerators prior to the invention of modern condensers) many old fridges contain temporal portals to the eras of pirates, princesses and space wars. Adults just don't want you to mess up the space-time continuum (adults, being older, are more vulnerable to temporal fluctuation) so they put out propaganda like this. Just make sure the door is all the way shut once you're inside (so that the Einstein-Chomsky circuit is closed) and you're off to adventure! (suffocation)
OK, so apparently Mom was trying to frame that damn giant frog feller for her son's death by asphyxiation of poisoning. Unless she was hoping they'd both drop dead.