Watch The Big Bang Theory Season 12 Episode 20 Online. Best and Free Online streaming for The Big Bang Theory TV Show. We picked the best sites to stream s12e20. Simply pick a site below and click "Watch Now!" button next to it. Some of the links may be broken, please upvote the working and good links so other users see those links for The Big Bang Theory Season 12 Episode 20 s12e20 at the top of the list.