youtube watchers...?

Did you mean "what are some popular series"? Films by the user "FilmCow" are popular. He is the creator of the hilarious 'Charlie the Unicorn', and 'Llamas with Hats' videos. 'Salad Fingers' is also well known. I think there is a series called 'Happy Time/Tree Friends'. A violent animated comedy where adorable animals are constantly getting injured. Other than those, I'm not really sure. I think there is a way to search on youtube for popular videos.