You can get those programs where once you have recorded some sound (voice) you can apply filters to it, so you can make your voice sound like a robot, deep voice, convert male voice to female and vice versa. You might want to try one of those
Can't remember a name for them but I've seen a few different programs that can do that, think even dell laptops come bundled with such software (cam software).edit:
a quick google search reveals that this program
can do the above. Theres many others available too.