When Neil Armstrong and Buzz Aldrin first attempted to pilot their lunar lander back off the moon, a critical switch broke, forcing the astronauts to improvise a solution with a ballpoint pen. Aldrin took responsibility for breaking the switch, but he was also the one who found the solution in a ballpoint pen.
Armstrong and Aldrin touched down in the lunar lander, Eagle, while their crewmate Michael Collins piloted the Apollo around the moon. Once Armstrong and Aldrin finished their tasks on the surface of the moon, they were supposed to fire up Eagle's engines and rejoin with Collins and the Apollo in order to return to earth. Looking at the lunar dust on the floor of the lander, Aldrin noticed a piece that stood out: a broken end of the ship's circuit breaker.
The US government had a plan in the event of a disaster: cut the television feed immediately. Fortunately, this wasn't needed, and the crew landed safely back on earth.