Weird pixelated lock screen with time

[AC Question]

So I thought this was just a glitch, but when my HTC (M9 I think) is near a magnet, it gets this very strange pixelated lock screen with the time on it, and I can only unlock it by getting it away from the magnet. However, today that same pixelated lock screen had a Halloween theme!! (I have screen shots, but don't have the option to add them here.) Any ideas??