Cabin in the Woods DLC for Left 4 Dead 2 once planned

Attentive horror fans may have spotted the bilious Boomer and other Left 4 Dead monsters snuck into Joss Whedon's delightful scare 'em up movie Cabin in the Woods, but L4D's involvement was once supposed to be far greater. Director Drew Goddard has revealed that a CitW expansion was planned for Left 4 Dead 2, but sadly got scrapped. Plainly, this post contains spoilers for the film, which you really should see if you haven't.