In the year 1500, Chinese bureaucrat Wan Hu attempted the first manned rocket flight by strapping hundreds of fireworks to his chair and lighting the fuse. He lifted a few feet off of the ground, and quite reasonably exploded. Roughly 500 years later, with the help of centuries of careful consideration and all the industriousness of mankind's collective genius, NASA sat down with intricate blueprints, cutting-edge technology and the greatest minds of the day, and said, "Hey, what ever happened to that rocket chair thing?"
This is the Lunar Escape System (LESS).
Not this. This is just a Chinese man exploding.
A sprocket of engineers (that's what you call a group of them -- we looked it up) called the Apollo Applications Program were planning a series of long-duration moon stays, and got all the way to the design stage before NASA pulled the plug. But the blueprints were already complete: AAP had laid out everything for these extended trips to Earth's moon. Even an escape system, should the lander fail after idle weeks spent on the abrasive lunar surface.
In the event of a lander failure, instead of curling up into a ball and seeing how many tears moon dust can absorb (Hint: It's zero. They just pool in your face mask), you could unpack the Lunar Escape System from beneath the ship, assemble it like an IKEA bookshelf, then siphon off fuel from the lander and strap yourself on.
"Oh dear God, the Allen wrench is missing!"