According to an old Irish legend, St. Patrick and St. Bridget struck a deal in which women would be permitted to propose to men every four years on Leap Day. That tradition continues on YouTube.
This is the nerdiest thing you'll see all day. If you want to make a lasting impression on your soon-to-be fiance, you need to propose in a creative way. Well, this isn't that creative, just your basic 'down on one knee' approach. But they were at comic-con which makes them nerds (not that there's anything wrong with that) so you can imagine the nerdgasm that happens at the :33 point of this video