With a trailer, TV spot, and a handful of posters, fans have only seen the tip of the iceberg of what Birds of Prey (and the Fantabulous Emancipation of One Harley Quinn) has in store. Even then, it's clear that the film is preparing to bring something new and unexpected to the world of superhero movies, with a pretty strong sense of aesthetic in the process. While there's still a lot around the film that remains a mystery, one detail - its soundtrack - is beginning to fall into place. Over the weekend, rapper and musician Doja Cat took to Instagram to announce that her upcoming song "Boss Bitch" will be tied to Birds of Prey. This was accompanied by a series of behind-the-scenes photos, two of which show her holding the iconic "Good Night" baseball bat.