Rhianna's "Umbrella" was written for Britney Spears.

It's not like Britney could have used a smash #1 hit....Uhhhhh.....Bwahahahaha!
Rhianna’s number one smash hit song, ‘Umbrella,’ was originally written for Britney Spears, according to reports.
The revelation has emerged after the song’s creator, American music producer Tricky Stewart, told another one of his artists that Britney Spears never got back to him about the track, reports WENN.
Singer and songwriter Taio Cruz revealed: "I was working with Tricky in his studio the day he finished Umbrella. As soon as I heard it I said, 'That is a smash, I have to have it,' but he told me it was on hold for Britney.”
Cruz added: "He waited but Britney's people never called him back."
Umbrella went on to become a cult smash for Rhianna earlier this summer, becoming the longest running UK number one of the decade - eventually holding the top spot for ten weeks.