@Admiral:
For one, they have the same unique style of fingers; and for two, they all have a skull for a face which may or may not resemble a poison symbol. For three, there has to be some good reason for why Magellan is the chief of Impel Down, and if he can create (or enhance) such creatures with his powers then that's a hell of a good reason. Also, we don't know where those dudes came from, but they all obey rules of the place for some reason…
For all these reasons and more, I think Magellan probably summons, creates, or controls the Bullgory/Blue Glory dudes!
You know, (Bear with me here) that really does make sense if they were based on the plant/flower "morning glory" also known as "Heavenly blue", which also happens to be…. Poisonous! Get it? Heavenly Blue, morning Glory… http://www.ces.ncsu.edu/depts/hort/consumer/poison/Ipomotr.htm … there's the proof, case closed.
Bah, who am i kidding, enough fooling around for one day.