Now they've got really, really, really bad blood.

A photo posted by Taylor Swift (@taylorswift) on

Although it hasn't been released yet, Katy Perry registered a trademark for a new song called "1984," which people think might be a dig at Taylor Swift and her 1989 album.

As anyone who's been following world events for the past few years knows, the two pop stars have an ongoing rivalry. They have an ex in common (John Mayer), they've battled over back-up dancers, they've written songs (likely) about each other, and they've accused one another of mean girl tactics.

And now the title of Perry's new song sounds a lot like the title of Swift's most recent album (and both are the years the singers were born). Could it be a scathing parody? And will it be as biting as Katy Perry's Superbowl swimwear?

Sources: Mashable