Interestingly enough, one early Apple II-era input method for Chinese would generate the characters on the fly (since the hardware at the time couldn't handle storing, searching and rendering massive fonts) meaning it could generate partial Chinese characters or ones that didn't actually exist.

http://en.wikipedia.org/wiki/Cangjie_input_method#Early_Cang...

In the Wikipedia article it even shows an example of a rare character that's not encoded in Unicode but which can be represented using this method.