If you’re not familiar with the site, Rap Genius lets users annotate specific parts of lyrics to any rap song with definitions that explain the meaning behind the words. Andreessen Horowitz explains their investment as, "embracing the potential in the site’s ability to annotate things beyond rap music such as poetry, political speeches, science papers, etc."
Yesterday, Groupon laid off their CEO and co-founder, Andrew Mason. Mason released a heart-felt goodbye letter online shortly after that was full of quirky phrases and references. Andreessen Horowitz saw this as the perfect opportunity to showcase Rap Genius’s ability to annotate beyond music and annotated the former CEO’s entire goodbye letter. The result is surprisingly informational and entertaining.
Above is my favorite explanation of Mason’s Battletoads reference. You can check out the full letter with all the annotations here on Rap Genius.