It always made me feel that no generation of MLP ever had any main characters, but rather major characters instead. I only say this because to qualify as a main character, they would usually appear in pretty much every episode. However, that doesn't seem to always be the case, which is why some are considered to be rather major characters in that they appear for the most part, but still have a handful of episodes where they don't appear at all. For example, Megan Williams and possibly Spike were considered major characters for MLP 'n Friends, while Twilight Sparkle was seen as a major for MLP:FiM yet still had a good number of episodes where they didn't appear at all. I never got why Hasbro did it that way for each of the series. Perhaps, some of you can tell me why they decided to not to have any actual main characters in any of the series.