One reason is the contrast between their characters. Spike is a dragon with a kind heart, and Starlight Glimmer has her own complex backstory. Their interactions can be really interesting. For example, Spike can bring out the lighter side of Starlight Glimmer, and she can help him become more confident in different situations.
You can start by looking on popular fanfiction websites like Fimfiction. There are often numerous stories featuring this pairing. Another good place is Archive of Our Own (AO3), which has a large collection of My Little Pony fanfictions, including Spike x Starlight Glimmer ones. Some of these fanfictions explore their relationship in different ways, such as adventures they go on together or how they help each other grow as characters.
Yes, there are quite a few. You can start by looking on popular fanfiction websites like Fimfiction. Some of them explore unique relationships between Starlight Glimmer and a human character, often with interesting plotlines that involve her magic and the human's worldviews colliding in a fictional Equestria - like setting.
Friendship is a very common theme. Since in the My Little Pony world, friendship is highly valued. Their relationship often starts from a place of rivalry or misunderstanding, but through various events, they become friends. For example, they might help each other in a magical quest or face a common enemy together.
One great Starlight x Spike fanfiction is 'A Magical Bond'. It explores their unique relationship in a world filled with new adventures. The story beautifully portrays how they support each other during difficult times.
You can try fanfiction websites like Fimfiction. It has a large collection of My Little Pony related fanfictions, including many about Starlight and Spike.
The cultural clash. A human has different values and ways of life compared to Starlight Glimmer. When these two meet in fanfictions, it creates a lot of potential for interesting stories. For example, a human's view on friendship might be different from what Starlight Glimmer is used to in Equestria.
Some fanfics might have a theme of self - discovery. Both Starlight Glimmer and Trixie have their own insecurities and areas for growth. In these fanfics, their relationship with each other helps them to discover more about themselves, like Starlight learning to be more confident from Trixie's bravado or Trixie learning about the importance of true friendship from Starlight.
One common theme is friendship development. They start as acquaintances or even rivals and then gradually become closer friends or more. Another theme could be adventure. They might go on an adventure together and through that, their relationship deepens. There's also the theme of self - discovery, where they help each other figure out things about themselves.
I'm not sure specifically. Fanfiction can be found on various platforms like FanFiction.net or Archive of Our Own. You would need to search those sites using the keywords 'Starlight Glimmer pregnant' and then check if there are any works that meet your criteria and are also appropriate in terms of content.