No — there is no official Castle Crashers PSP exclusive ISO released by the developer. Castle Crashers was originally released for Xbox 360 in 2008, later ported to PlayStation 3, Windows, macOS, Xbox One, Nintendo Switch, and mobile in various forms, but there is no legitimate PSP release.

Stop chasing the PSP ghost. Buy the game on Switch or Steam Deck. Support The Behemoth. And let the legend of the "exclusive" PSP ISO finally rest in peace.