No PSP, PS Vita, or mobile version exists. Any website claiming to have a "Castle Crashers PSP ISO" is either:
: Sites offering "verified" ISOs for games that don't exist on a platform often distribute malicious software. i castle crashers psp iso verified
Searching for “i castle crashers psp iso verified” puts you in the crosshairs of malicious actors. Here is what typically happens when you click those links: No PSP, PS Vita, or mobile version exists