Mac不 (Macfu; NON-MAC) - Refers to how she is the "anti-Mac" UTAU. The kanji is actually supposed to be used as a prefix, but supposedly the creator used it as a suffix on purpose.
|TYPE: JOKALOID2 (UTAU)|
MODEL: JK - Possibly a reference to the chat-speak that means "Just Kidding".
G3-C6 @ 80-150bpm
Bruised/Rotten Apple (fan item)
Cherry (assigned item)
|HEIGHT / MEASUREMENTS||163cm (5ft 4in)||VOICE SOURCE||Macnenai||PICTURE LINK LIST||CONCEPT ART|
|BIRTHDAY||June 1||LIKES||Windows OS and Microsoft products||MEDIA LIST||???|
|RELEASE DATE||June 1, 2010||DISLIKES||Mac OS and Mac products||SIGNATURE SONG||???|
Her voice can be downloaded from her official page.
Fifi was originally a scheme to trick users into downloading her by claiming that she was actually Nana Macne's voicebank; however, when clicked, one could see clearly that she was very much NOT Nana at all. Some people actually like Fifi and have chosen to use her voicebank. The true author of Fifi remains private to avoid legal pursuit, apparently. Would probably be blacklisted if the author did not quickly revert Fifi's voicebank to be exposed as fake. Has very clear pronunciation.
Her trap videos have been taken down, allowing her to escape the Blacklist once again.
Fifi did manage to make the 7th Newcomer UTAU award in Nico Nico Douga's UTAU Ranking for July 10-17, 2010. 
Some details are based on existing information and usage experience. The details seen here may be subject to change without prior notice.