Kratos doesn't want to talk about him time in PlayStation All-Stars Battle Royale
God of War: Ragnarök made the PS3/PS Vita game canon.
If you had a PlayStation 3 or a PlayStation Vita, there's a chance you may remember Sony's take on Smash Bros., a title known simply as PlayStation All-Stars Battle Royale. The game brought together many iconic PlayStation characters and pitted them against one another in fights. The protagonist of God of War: Ragnarök, Kratos featured in this very game, and in his most recent outing, he has been directly asked about that very experience.
During an interaction between Kratos and Mimir, the talking head asks the Ghost of Sparta about his time battling "beasts, scoundrels, princesses, the undead, automatons and... history's greatest musician," to which Kratos replied, "I would not speak of this."
This daft and short interaction is technically enough to make PlayStation All-Stars Battle Royale canon in Sony's game universe, and does to some extent mean that Ratchet & Clank, Jak and Daxter, Nathan Drake, and so on, all exist in the same universe. Crazy.