He even apologizes for not being able to fit every single source video in, and calls out viralogist Tay Zonday’s cover for special (non-inclusion) mention.
On a technical level, Gotye even shares the details of his toolkit, “I used KeepVid.com to download the YouTube videos, Ableton Live for audio stretching, pitch-shifting and the initial video editing, and Adobe’s After Effects to put the final video together.”