Grimes was at the Met Gala last night, and she turned up with a surprising guest – billionaire capitalist and SpaceX founder Elon Musk.

Musk appeared on the red carpet wearing a white jacket and Tesla pin, while Grimes wore a black dress with a Tesla choker(!). According to Us Weekly, the pair designed the dress together “over dinner” then commissioned a team to make it.

A few hours before the event, Page Six reported that Grimes and Musk have been “quietly dating” for a month, having met online over a niche, nerdy joke. Musk had planned to tweet a pun about ‘Roko’s Basilisk’ (a thought experiment considering a future where AI overlords torture mankind eternally) mashed up with the word ‘Rococo’ (the ornate baroque art style).

As it turned out, Grimes had made the joke three years earlier with her character Rococo Basilisk, who appears in the video for “Flesh Without Blood”. According to Page Six, Musk reached out to Grimes after seeing the video, and she responded by saying it was the first time anyone had got the joke. Last night, seemingly in anticipation of the report, Musk finally tweeted the joke out to his followers.

Earlier this year Musk tweeted out a Grimes video, calling it the “best music video art I’ve seen in a while.”

Naturally, the unlikely pairing led to some funny reponses on Twitter. Check out some of the reactions below.