Usually in hectic office environments an unsuspecting poor sap will leave his computer unlocked for a just a few precious minutes. Within this time the more saavy co-worker has Carte Blanche access to google up a pic of a hot pair of gay men embracing in a clutch of passion. Or in extreme cases a well placed schlong dangling pic right on his desktop.
The coup de grace of this prank is to conceal the background with a few legitimate applications such as Word, Excel or Outlook email.
Upon returning to his workstation he may work hours before minimizing or locking his workstation down (much too late) to be shocked to see a pink pile of man junk proliferate his screen. This works exceptionally well when female hetero passers by notice the commotion from his cube.
Betty: "How many times are you going to give him a Screengayver Ted?" "LOL"