Ok this isn't exactly a healthy 12,000 calories, but once I started typing my imagination went loose:
A big banana split (calcium, potasium, protein from the nuts!)
A steak in a pool of butter like at Ruth's Chris and garlic mashed potatoes
A big burger with french fries and a real coke
A breakfast with bacon and sausage and eggs and hashbrowns
sourdough bread WITH butter on it
A salad with full fat ranch on it
A huge piece of warm chocolate cake with whipped cream and heck make it a la mode
Ok, this probably isn't quite 12,000 calories, but perhaps close. And my body would fully reject this food if I tried to eat more than one of these things.