Special effects help - making circles/squares appear???

So, I was looking for some help with another special effects aspect. You've probably all seen those videos that have the random rectangular bars roll across the screen with characters in it, or the random circle or square that pops up with a characters face in it while a scene is happening. I would really like to use that effect in my latest video but I have no idea how to do it. If you need clarification on what it looks like, watch the below video.

Is this what you mean? Using the cookie cutter?

Thank you so much