Someone on TikTok showed how you can steal a massive chunk of someone's pizza without them knowing it. You just have to be the one who cuts it.
Basically, they cut out a huge slice that spans the entire diameter of the pizza starting at one side, and going the whole way to the crust on the other side. Then they slide the two remaining chunks of pizza together.
It's an oval at first. But once they cut it into slices, it's pretty hard to tell.
(The original video was taken down, but here's a repost on YouTube and a screenshot.)