An easy way to download YouTube videos as MP4 files: throw this bookmarklet up in your browser’s bookmark bar, then click on it when you’re on a YouTube video page that you enjoy.
“Self-fusing; 700 PSI tensile strength; insulates 8,000 volts per layer; withstands 500 degrees F of heat; flexible to -85 degrees F; never gets gummy or sticky; resists fuels, oils, acids, salt water, & UV rays.”