a 12 lb chicken,are ya sure it wasn't a turkey 
those Purdue Oven Stuffer Roasters are really big. I was just looking online, maybe not that large. I saw one reference of 6-8 lbs. I thought they were larger then that.
I guess 6-8 lbs is a pretty dogum big chicken to begin with. What do I know about chickens!
I just cook 'em and eats'em.
Speaking of
Anybody ever hear about Mike the Headless Chicken?
It happened Fruita, Colorado in the 1940's and its fer'real! (they even have a Mike the Headless Chicken Festival every year)
http://www.miketheheadlesschicken.org/story.html
