Remember Sony's Smash Bros. clone PlayStation All-Stars Battle Royale? A tidbit of dialogue in God of War Ragnarok has essentially made it canon.
Look, let's get this out the way. We all hate PlayStation All-Stars Battle Royale. It's name is silly and long, the super system just doesn't work, and it featured the wrong Dante (though some of the stages were really fun, looking at you Loco Roco x Metal Gear Solid stage). If you hate the game but love God of War, then I've got some bad news for you unfortunately: PlayStation All-Stars really happened.
In a recent clip shared by TheCardinalArts on Twitter, dad of war himself Kratos is asked by Mimir about a 'tournament' he once took part in. Kratos notes that, obviously, he "fought in many contests," but Mimir specifies that in "this particular one, I heard you did battle with beasts, scoundrels, princesses, the undead, automatons and… history’s greatest musician. That’s not… that’s not true, is it?" Kratos in kind responds, "I would not speak of this." To which Mimir, and everyone else in the world, says "Fair enough, brother."
Some fans were wondering if this is actually a reference to Krato's appearance in 2011's Mortal Kombat, as they believe the world's greatest musician line is talking about the character Rain. However, Press Start was able to confirm that it is in fact a reference to PlayStation All-Stars from Ragnarok's narrative director, Matt Sophos. So obviously the world's greatest musician could only be a nod to PaRappa the Rapper (the world's greatest musician).
This confirmation opens up a whole can of worms though. Can the sweet, innocent Sackboy really exist in the same universe as a man that tears down his enemies without any kind of remorse for his actions (I'm doing a little bit here because I'm talking about Nathan Drake (he really does kill a lot of people and the games just don't address it)).
Who am I to judge the canonicity of something though? I'll take anything that could possibly bring back Kat from Gravity Rush (even if she was a DLC fighter that will be quite difficult to get now).