Call Me Maybe Star Wars was an excellent example of remxing combining the beat and music (not singing) of Call Me Maybe, with clips from Star Wars where the character say the lyrics. This falls under fair use because 1) duration of the clip are small (one word) 2) the song was parody.
YouTube Duet was the most amazing thing I’ve ever seen! I love that someone could take two youtube video and just play them and it works as one piece! The first song with Kermit the Frog was probably a paradoy , and th esecond one was a live recording of Miles Davis. It was beautful an really clever. The video falls under fai use becasue 1) the song was probably a parody 2) the second song was fundamentally changed by first song becasue it was dominate.
“Don’t Tase This” was cute and clever. It too fall under fair use because 1) the song is only being used in clips 2) the video clip is from the news. I think that line between copyright and fair use is so blurred. However, it seems clear that the smaller the segment and the more editing you do it it the safe you will be.