Kirkland Light is an off-brand beer sold at Costco. It has nowhere near the commercial visibility of Bud Light, or any other lower quality lager, but its obscurity and copious quantities -- it's sold in 48 packs -- has fashioned it a cult favorite among people unconcerned with taste.
It's likely that you hadn't heard of Kirkland's beer, given the company's lack of advertising, until a man with a YouTube account named Randy Colpek decided to whip up a couple of slogans for Kirkland Light, his favorite beer.
In the commercial (it's a faux commercial, really) avove, Randy, who is possibly a few beers deep, sets up a veritable fortress of Kirkland Light boxes and crashes through them like the cheerleader the brand never deserved. He proffers all sorts of dumb catchphrases and mottos, a few of which are genuinely funny and might sell some beers before completely ruining Kirkland's reputation, which to date is unsullied. Some are slightly NSFW, language-wise.
The video, which was filmed last August, didn't really take off until Colpek posted it to Reddit and took a few questions about it. He explained that he is indeed a Kirkland Light super fan, and is probably worthy of a lifetime sponsorship solely based on his brand allegiance alone.