Mice that were exposed to heavy metal became aggressive and murderous

One study conducted by David Merrill exposed mice to heavy metal 24 hours a day. The band chosen was Anthrax. The purpose of the study was to see how the heavy metal would affect their ability to learn new things.

Shockingly, the experiment could not be finished because instead of completing the Maze, the heavy metal mice all killed each other.
In further experiments, Merrill exposed the mice to heavy metal for only 10 hours a day. Even though the mice did not become homicidal in this experiment, they were much worse at solving the maze than when they had first encountered it.

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A complex series of tunnels runs beneath Walt Disney World.

Walt Disney was concerned when seeing a Frontierland cowboy walking through Tomorrowland. Unimpressed by this breaking of the 4th wall, Disney recognized there needs to be a way to keep certain things out of sight from the general public. Thus, underground tunnels were added to Disney World. That way trash and utilities can be hidden and costumed performers can move around outside of public view when they are not on duty. 

This massive tunnel system contains corridors that are 15 feet high and wide enough for delivery trucks to drive through. There are also locker rooms, maintenance rooms, cafeterias, and a fire prevention center. There are 28 hidden stairwells to get to the tunnel system. Children under 16 are not allowed in, so as not to spoil the magic of their Disney World experience. 

Read all about the Disney Tunnel System, including where the entrances are!