I don't know which specific game or card game Yu-Gi-Oh zexal refers to. If I can provide more information, I will try my best to answer your questions.
A 'big dick morph story' could potentially be a fictional or fantasy story where a character undergoes some sort of transformation related to having a large penis. However, this is a rather vulgar and inappropriate concept in most contexts.
The'morph girl story' could potentially be about a girl's journey of transformation, perhaps not just physically morphing but also in terms of her personality or life situation. Maybe she discovers she has this unique ability to morph and has to deal with the consequences and challenges that come with it, like hiding it from others or using it to help people.
Well, 'gay morph stories' can often involve transformation not just in terms of self - discovery but also in appearance. There might be a story where a gay man decides to change his style completely to match his new - found confidence. He goes from dressing conservatively to expressing himself through flamboyant and unique fashion, which is a form of morphing in a way that reflects his inner self.
Since I don't know the exact'morph girl story', I can't say for sure. But it's likely that the morph girl herself is a main character. There might also be her friends or family members who play important roles, perhaps some who are aware of her morphing ability and some who aren't.
The 'kid muscle morph story' could potentially be about a child who discovers a special power or condition that causes their muscles to morph. It could be set in a world where there are unique biological or environmental factors at play. Maybe the kid lives in a place with a strange energy source that affects muscle growth and development in unexpected ways. The story could explore the kid's experiences with this new muscle - morphing situation, how they deal with the physical changes, and how it impacts their relationships with others, like their friends and family.
Acceptance is likely a theme. The story may show how the characters, both the ones who morph and those around them, come to accept the new forms and identities, which could be a metaphor for accepting gay people in real life.