Board Thread:General Discussion/@comment-24269730-20140308162509/@comment-5060080-20140330210005

Alien X can't have an Ultimate, because his species is already pretty darn Ultimate. Bellicus and Serena are only in Alien X, and species evolve as a whole, so it's impossble for him to evolve out if Bellicus and Serena if no other of those species have it.