The game’s last season was a multimonth Marvel mashup, there have been multiple Star Wars- themed cosmetics, other real-world streamers added to the game include Tyler “Ninja” Blevins and Kathleen “Loserfruit” Belsten, and there have even been concerts (and accompanying in-game cosmetics) featuring huge artists like Travis Scott and Marshmello.
Crossovers like these are by no means a new thing for Fortnite.