Since there is no official PSP version, your best bet for a smooth experience is playing the official Remastered version on current platforms.
Castle Crashers , the beloved 2D arcade-style adventure from The Behemoth, has entertained millions with its chaotic combat, quirky humor, and co-op gameplay. While many players search for ways to play it on portable devices like the PSP, it’s important to know the official options available today.
Years ago, a talented developer named cthugha began work on a fan-made "Castle Crashers" clone for the PSP using the LUA engine. It featured the basic art style and some early levels but was never a complete game.