If you downloaded a file named Rick.and.Morty.S06E01.1080p.WEB-DL.VP9.Libvpx.Opus.mkv – you have a high-efficiency encode, not a special version of the episode. Enjoy "Solaricks" – and pay attention to the Mr. Frundles post-credits scene.

Libvpx is an open-source video codec developed by Google (based on VP8 and VP9). It is not a show, a character, or a secret plot device in Rick and Morty .