When Joseph Joestar and Gintoki Sakata meet, they start commenting on how they sound the same. This is because both Joseph and Gintoki are voiced by the same actor Tomokazu Sugita.
The game was made to commemorate the 45th anniversary of Shonen Jump magazine, and features characters and settings from various Jump manga comics.
Jotaro Kujo and Dio Brando from Jojo's Bizarre Adventures, Dai from Dragon Quest: The Adventures of Dai along with Yoh and Shaman King were planned to appear in the game Jotaro, Dio and Dai were all gonna be playable while Yoh was gonna be a support only character, all 4 characters were found within the game's files it is possible they were cut due to time constraints.
Jotaro Kujo and Dio Brando from Jojo's Bizarre Adventures, Dai from Dragon Quest: The Adventures of Dai along with Yoh and Shaman King were planned to appear in the game Jotaro, Dio and Dai were all gonna be playable while Yoh was gonna be a support only character, all 4 characters were found within the game's files several text strings in the ISO refer to these character's textures, it is possible they were cut due to time constraints or were gonna be add in as possible DLC.