Stratt telling Grace that he's perfect for the mission because he doesn't have a family or even a dog and he panics and goes "Uhhh actually I have a fiance. Yeah. He just proposed to me a couple of days ago. So I'm getting married."
He gets home to his best friend/roommate Simon and says "Hey man so my boss wants to send me into outer space so I lied and said that you proposed to me haha! Whoops!"
Grace thinks that Stratt will take pity on him and leave him on Earth but instead she ALSO kidnaps Simon and sends him into space along with Grace because she worries that Grace's memories will return and he'll freak out when he realizes that he'll never see his husband again.
Cue Simon and Grace waking up in the Hail Mary and going through pictures that show them having a wedding ceremony and they're like wow. My husband.
They spend months in the Hail Mary fucking each other's brains out before they remember what actually happened but by that point they're so genuinely in love that they don't even care.
for some reason it reminds me of this meme:
except in this situation it would be "yo i don’t have time to explain but we have to get married"