The Muggleborn poster thing happened. In Harry's room, Dean hung a West Ham football club poster and it mystified Ron. He poked it with his wand, trying to get the players to move.
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A Potterhead would know that.
I remembered that happening in the books, but I think this post is talking about say, someone literally covering their entire room in posters of muggle celebrities, instead of just one.
Theoretically, if they could somehow create a spell that negates the effects of magic within a certain area (not necessarily the magic itself, just the effects they have on electronics), then they could get a router and have wifi
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A Potterhead would know that.