When I attach an item frame to a block and then breaks the block, unlike the sign, which pops off immediately, the item frame remains there for about three to four seconds before popping off.

I discovered this next bug when I was just placing random blocks and skeletons:
When a skeleton fires an arrow at the item frame, the item frame pops off and so does the thing inside it. The fired arrow disappeared. Very weird indeed. I then tried to fire an arrow at the item frame by myself and the same happened. These both happened in survival. Then I switched to creative mode and fired another arrow at the item frame. This time both the frame and its content just disappeared, and so does the arrow.

I think this is probably caused by the fact that the item frame is treated as an entity. However isn't it just too weird to see an item frame disobeying physics and just hanging in mid air for a few seconds? Also isn't losing your arrow after shooting it at a display frame hanging on the wall just same as weird?