You know what will happen in The Ultimate Enemy: Part 2? Vilgax will absorb Diagon's power and will turn into a freak monster mutated with two other species. Firstly, Vilgax+Diagon is like the New iPad and Vilgax looks like the iPad 2. Yup, no facial differences that hint that Vilgax is Diagon, unless you count the part where Vilgax changes size to defeat Ultimate Way Big. Lets all cross our fingers and home the episode will tell us more.