John and Hank have posted a number of videos on the topic of animal mating. They have seemed most fascinated by the mating habits of anglerfish, giant tortoises, and giraffes. Giraffe mating, termed "giraffes who love giraffes," has since become a popular meme within nerdfighteria.

After noticing that the most viewed vlogbrothers video had a thumbnail of two giraffes having sex (titled "Giraffe Love and Other Questions ANSWERED," uploaded Jan 3, 2009), this became a topic of discussion that culminated in Hank performing a song titled, "People Who Love Giraffes Who Love Giraffes."