I was playing around on a creative superflat world. I'm not sure if it's important or not, so the details of the world are as follows:

• 1 grass, 40 dirt, 1 bedrock
• Structures turned on
• Mob spawning turned off
  While spamming a bunch of foxes and messing about with the weather and time, I noticed something. If i did /time set night and /weather thunder, all the foxes would start running towards one specific spot, crowding each other to the point of suffocating. Once it turned day, or the thunder stopped, they would return to their normal AI.
  I let the foxes out of the cage they were in to investigate, and it seems like they're all running towards 0,0. Once they get there, they crowd it, forming a huge mob centered around the coordinate. Naturally extremely confused, I told others about it, and they experienced the same thing. I'm not exactly sure what causes this, but it's very weird.

EDIT 1: It seems as if the time doesn't matter. If the weather is thunder, they will run towards 0,0, regardless of what time it is.

EDIT 2: I loaded up another world exactly like this one to take an F3 picture, but instead of moving towards 0,0, the foxes just completely stopped moving at all. Every adult fox was standing completely still. They would attack chickens and rabbits when the prey mobs were spawned nearby, then go back to standing unmoving, not even rotating (although their heads would move to look at the player and other mobs.) It seems like something about thunderstorms and superflat worlds just make foxes go crazy?