re: If you had to eat 20k calories in a day to save your life

Chocolate is one of the most calorie dense foods there is that is pleasant to eat. It's why the military loves to put that stuff in emergency survival rations. You're looking at about 250 calories for your average candy bar, so you'd need to eat about 80 candy bars in a day.

I'd go with a big arse pile of good chocolate bars and some cold milk to wash it down.

ETA: Pure fat is pretty much the most calorie dense thing you can eat at 9 calories per gram, so you could just eat about 5 pounds of lard and get it done.