Die Antwoord, the South African "rap-rave' counter-culture group, were approached by Lady Gaga to open for her tour, and turned the offer down. At some point, Gaga was told that Die Antwoord were fans of her; how this point and them turning the tour down turned into them lampooning Gaga in their "Fatty Boom Boom" video (including a scene where the Gaga-imposter is rocking the meat dress and giving birth to a prawn) is anyone's guess.
Gaga's tweets after the video were her hyping up how she'd sold 100,000 tickets at a gig, and that while they claimed they were fans, she knew the truth, and they weren't "little monsters." Die Antwoord kept it calm, and let her know that while she might be a bigger star, she's not as cool as them. Since this display, no prawns have been thrown.