Charli explained to Apple
that after they'd recorded "1999," she suspected Sivan "wanted to get a little bit weirder than we got," as she'd heard him mention he was into her experimental mixtape Pop 2
. She added: "After '1999' came out, I hit him up again and said, 'Should we just go there? Should we just go out of space? Like, let's do a weird moment.' And he was like, 'Yes, let's do it.'"