Morgan Freeman, host of Through the Wormhole on the Science Channel, has a trademark baritone voice. What is better than listening him explain the most complex ideas about the Universe in a voice that is smoother than silk? Hearing him do it on helium.
Why does inhaling helium make voices sound hilarious? The density of helium is lower than nitrogen, so when a person who has inhaled helium begins to speak, the gas affects the wavelength of the sound waves coming out, allowing them to travel more quickly. Thus, the result of inhaling helium is a temporary squeaky voice, reminiscent of Alvin and the Chipmunks.