My most popular video is my press video for Comic Con back in May 2016. I met and filmed a lot of people and uploaded it just after the event so people would have been searching for it.
My second most popular video, which is actually related to the content I now produce, is a video I made on Victorian slang. I don't know what made it more popular than other languages I've done, but there are some great words in there so I'll certainly take it!