Midna did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Although not confirmed as one of the Princesses of Fate, Midna is still a princess that appears and gives various tips to the rest of the princesses. She was confirmed in the game at the release of the Twenty-Second Choice trailer.
Midna makes her first televison appearance in Pikachu and Kirby: Amazing Adventures, and is Pikachu's main love interest. She mainly appears in her human form. Pikachu instantly falls in love with her while she is unaware. She enjoys his company and even begins to develop feelings for him because of kindness and ambition, something she could never find in any other person she's ever dated.
Midna makes a minor appearance in the Wii U/3DSSuper Smash Bros. title Super Smash Bros. Fusion. In the game, she appears on the back of Wolf Link while he is in battle, and also allows Link to transform into said wolf form. She also uses her magic to aid the wolf-Hylian in battle. In Wolf Link's taunts, she is the main focus for many of them, with her sarcastic personality taking over from Link's strong and silent demeanour.