Brain Hemispheres
Brain Hemispheres
[Cueball is shown with the right half of his brain (on the viewer's left) colored in orange and the left half (on the viewer's right) in iris blue. An iris blue box is overlaid over the right half of the  body (on the viewer's left), and an orange box is overlaid over the top half. The boxes are overlapping in a greenish color on the upper right quarter of the body (on the viewer's left).] Neuroscience Fact: [An arrow pointing to the iris blue rectangle on top with the text above:] The left half of the brain actually controls the right half of the body... [An arrow pointing to the orange rectangle at the right, the text reads:] ...while the right half of the brain actually controls the top half of the body. [An arrow pointing to the overlapping area (the top left body from the viewers perspective) with the text below:] Disputed/dual control [An arrow pointing to Cueball's left leg area (on the viewer's right), not highlighted by any color, and the text is:] This leg is fully autonomous

As a general rule, each cerebral hemisphere controls the opposite side of the body; things on the left half of the body are controlled by the right side of the brain and vice-versa. Biology is complicated, of course, so as with most biology "rules" there are exceptions, such as the cranial nerves , but it's true for most motor functions, and a relatively well-known factoid, if not strictly correct in all cases.
Randall spoofs this by saying that rather than controlling the left half of the body, the right brain controls the top. This leads to a Venn-diagram-like picture of the human body, with an overlap in the upper right, labelled "disputed," echoing maps that display a territorial dispute , suggesting that the halves of your brain fight for control of the region, or " dual control " like in an airplane, where the pilot and the copilot both can control the plane at any time. The reorganization also leaves a gap in the bottom left, implying that the left leg is not controlled by any part of the brain, and instead has a mind of its own.
The title text is another, separate joke about the same factoid. He proposes that the hands should be referred to not by their physical location, but by the hemisphere of the brain they're connected to. Of course, this is not only silly but inconsistent: if the hands were labelled by hemispheres of the brain, the same would presumably apply to the arms. Furthermore, there would be no reason to give left/right names to the hemispheres themselves, since their placement in the skull would be irrelevant.
[Cueball is shown with the right half of his brain (on the viewer's left) colored in orange and the left half (on the viewer's right) in iris blue. An iris blue box is overlaid over the right half of the  body (on the viewer's left), and an orange box is overlaid over the top half. The boxes are overlapping in a greenish color on the upper right quarter of the body (on the viewer's left).] Neuroscience Fact: [An arrow pointing to the iris blue rectangle on top with the text above:] The left half of the brain actually controls the right half of the body... [An arrow pointing to the orange rectangle at the right, the text reads:] ...while the right half of the brain actually controls the top half of the body. [An arrow pointing to the overlapping area (the top left body from the viewers perspective) with the text below:] Disputed/dual control [An arrow pointing to Cueball's left leg area (on the viewer's right), not highlighted by any color, and the text is:] This leg is fully autonomous
