This is obvious from the You Tube videos which go viral. They are not the Photoshop tutorials or even the band promos, they are the pranks and japes which tickle the viewer. Not only are they amused, they get a buzz from the gifting of the link to their friends. This is not a one-size-fits-all type of operation because the cute kittenss repeatedly falling off a sofa may split your sides but leave others cold. On the same score this is not a precise science, because no-one can predict what will go viral and what will not. All the advertiser can do is look at what has worked in the past and try to replicate it, hopefully with some creative input.
