Yo-yo tricks are already a miracle of physics. But Ben Conde specialises in a type of yo-yo with an unattached string called a diabolo, and does things that defy all logic. There's one sneaky feature that makes these contraptions work. Hidden between the halves of his yo-yo are tiny silicone friction pads. These -- combined with high rotational speed -- grab onto the string in midair and give it just enough of a tug to let it wrap back around the core. Thusly snagged, the friction increases exponentially, and the yo-yo flies back. It's a neat trick of physics, but it still makes it look like Conde made a deal with the devil.
Unfortunately, there's no fancy science or belt friction equation that explains why Conde is so much better at yo-yo tricks than most people. His secret is very boring hard work and practise.