H21K Sequence
It was a nonsense code from a boring TV show. Two guys bickered about it while fixing a spaceship. It also gave them a fake excuse to pretend they were friends before they got stuck on Mars.
'H21K is just a bunch of letters.', @notsmart
'I called my friend H21K to pass the test.', @testcheat
'H21K is the reason I failed math.', @mathfailure