Fifty years ago, Apollo 13 astronaut Jack Swigert forgot to do his taxes.

(oops)

With this momentous anniversary, people around the world are celebrating the mission that has famously been remembered as a "successful failure." But, as we recall the fast thinking from NASA Mission Control and the astronauts that ensured the Apollo 13 crewmembers returned home safely, we also think back to one of the less somber moments of the mission — the time when astronaut Jack Swigert realized he hadn't filed his taxes in time for the April 15, 1970 cutoff.

To be fair, Swigert wasn't supposed to be on Apollo 13; he was on the backup crew. But original crewmember Ken Mattingly was exposed to the German measles close to launch, and so NASA decided to swap the two to ensure that the crew wouldn't be infected. (Mattingly never ended up getting sick and flew on Apollo 16.)

Apollo 13 timeline: The hectic days of NASA's 'successful failure' to the moon

Apollo 13 astronaut Jack Swigert eats breakfast before launching on the mission, not yet realizing he's forgotten to file his taxes. (Image credit: NASA)

And because Swigert had to scramble to prepare after the swap, he (evidently) didn't file his taxes before leaving.

Approximately 24 hours and 18 minutes into the mission (and you can read the official and hilarious NASA transcript here ), which was well before the disastrous oxygen tank explosion, Swigert asked Mission Control:

"Uh oh; have you guys completed your income tax?"

Commander Jim Lovell, laughing, followed that up with: "How do I apply for an extension?"

Mission Control burst into laughter. Swigert replied: "It ain't too funny; things kind of happened real fast down there, and I do need an extension." And, again, he was met with raucous laughter.

Swigert tried again to explain his position: "I didn't get mine filed. And this is serious; would you." But Mission Control was still reeling, "you're breaking up the room down here."

The teasing went on a bit longer (and started to get more creative). The crew was, at this point, still planning on landing on the moon so, in jokingly suggesting that Swigert's misstep could interfere with the mission, someone chimed in to ask, "Is it true that Jack's income tax return was going to be used to buy the ascent fuel for the [lunar module]?"

Despite the ribbing, Mission Control assured Swigert that they would help him get his taxes filed on time. While Swigert was not in a different country, he was still considered a U.S. citizen abroad, which qualified him for an extension to file his taxes late but penalty-free.