I'm guessing this is parodying the part of FF7 where Cloud and the gang found a giant snake monster impaled on a tree by Sephiroth. That is most likely Solid Snake's famed cardboard box.
It is a reference to a scene in FF7 in which after leaving Midgar Cloud&party stumble upon a corpse of Midgar Zolom (giant snake, by this point of the game is probably way too powerful your average player to defeat) that has been, presumably, impaled on a tree by Sephiroth
