You know what you don't see too often in comics? Aliens that are truly alien. Most alien races are identical to humans except for one or two features, or they're evil inhuman creatures and nothing in between. Looking at Prospero here, you do see something different - the shape of the helmet, the proportion of the limbs is slightly off, helping to suggest a non-human nature. And because of his language issues, his behavior is the only indicator of his character, so it's left mysterious and well...alien at times.