Board Thread:Questions and Answers/@comment-11255996-20140312014418/@comment-3974711-20140312151340

You're thinking chronologically. Which is not appropriate becaus ethe transformations are categorized by show. Take Articguana for example. He became accessible to Ben when he was 16 (Omniverse) but in the OS was only ever used by Ben 10,000, twenty years into the future. But it's not right to categorize him as either an OV alien or a Future alien (not now anyway), becaus efirts of all he was introduced and shown in the OS.