Everyone knows the sound a rattle makes, and almost nobody knows what makes it. The blade is frozen a second before the answer, so the question sits open in your head. The only way to close it is to click.
How the packaging works
Title
The title asks the exact question the viewer cannot answer.
Thumbnail
The blade paused on the rattle shows the answer is one cut away.
Remix this
Use this when your topic has a familiar outside and an unknown inside, physical or not. Show the cut about to happen, never the opened result, because the reveal is the entire reason to watch.