The Japanese term "MAD" videos represent a super-set of what's called "anime music videos" in North America. Parodies, remixes, reanimation, juxtapositions, and theme compilation are also included under the fan video heading.
In a cute, and very popular (over 100,000 views is a week on Nico), new MAD by "Del Sol," the cast of Non Non Biyori is edited into the opening for Working!!
Bonus music video MAD