Square Enixs Kingdom Hearts series has always been known for its references to other IPs and franchises. Naturally, a series that mixes the Final Fantasy universe with that of Disney films is going to receive widespread attention for its crossover elements. As the franchise has continued to grow, Square Enix has not been shy about pulling from its history, notably bringing in characters from The World Ends With You in 2012s Kingdom Hearts 3D: Dream Drop Distance.