Remember when Shake Shack was just a modest burger stand in Madison Square Park? Danny Meyer's now-famous burger and milkshake chain has swept the nation, and before commuters get swept away by trains, they can pop into this Penn Station outpost in the lower concourse for an all-American bite. Expect beloved menu items like crinkle-cut fries and the Shack Stack, a cheeseburger topped with a Muenster- and cheddar-filled fried portobello mushroom. There's also Stumptown coffee and breakfast sandwiches for those making the morning commute. Shake Shack's simplistic goodness is probably the only thing those taking Amtrak, NJ Transit, and LIRR can agree on -- and that Penn Station is an eyesore.