Dib, for example, would probably be both horrified and intrigued. He might see it as another opportunity to expose Zim as an alien, thinking that this strange pregnancy is part of some evil alien plot. He would constantly be spying on them and trying to gather evidence. On the other hand, Gaz's friends might be more supportive. They would offer her advice on dealing with the pregnancy, like what to eat and how to stay comfortable. But they would also be a bit weirded out by Zim's involvement.
One common theme is the exploration of their relationship. Since they are two very different characters, many fanfictions focus on how they interact, whether it's in a confrontational way or a more cooperative one. Another theme is the idea of discovery. Gaz might discover something new about Zim's alien nature, or Zim might learn something unexpected about Gaz. And often, there's a theme of the extraordinary in the ordinary, like how their strange adventures play out in the backdrop of their seemingly normal neighborhood.
The appeal of 'Invader Zim Gaz x Zim' fanfiction lies in the contrast between the two characters. Gaz is this tough, no - nonsense girl, while Zim is this bumbling alien. When they are paired in fanfiction, it creates a really interesting dynamic that fans love to explore.
One possible plotline could be that Zim, in his bumbling attempts to blend in on Earth, accidentally ends up in a situation where he has to kiss Gaz as part of a dare or a misunderstanding. For example, maybe some of the school kids dare him to kiss the scariest girl in school, which is Gaz. Another plotline might be that there's some sort of alien or magical influence that makes them attracted to each other, leading to a kiss.
One common theme is the 'opposites attract' idea. Zim is so outlandish and Gaz is so reserved, and fanfics often play on that contrast. Another theme could be 'unlikely allies'. Since they are both sort of outsiders in their own ways, some fanfics have them team up against common foes.
Common themes could involve character growth within their relationship. Since they are different characters, the fanfic might show how they change as they get closer or face challenges together. Also, it could touch on the idea of acceptance, like accepting each other's quirks and differences.
A common theme could be friendship. Despite their differences, writers might explore how Gaz and Zim could form an unlikely bond. Another theme might be adventure, as they both have unique personalities that could lead to exciting escapades.
Perhaps there is some sort of magical or technological mishap. Let's say a device Zim was working on malfunctioned and affected Gaz in a way that made her pregnant. Gaz, being the tough one, is determined to figure out a solution on her own, but Zim, realizing the gravity of the situation, tries to make amends and help. They could go on a journey to find a way to reverse the process or come to terms with it and plan for the future together.
Gaz is a rather unique character. She is often seen as a loner, very much into her video games. She has a rather dark and sarcastic sense of humor. She doesn't really have a lot of friends and seems to prefer it that way. Invader Zim, on the other hand, is an alien on a mission. He is overly confident, but also a bit clueless at times. He is constantly trying to take over Earth but his plans are always thwarted in the most comical ways.
I'm not sure if there is specific 'invader zim gaz pregnant fanfiction' available. Fanfiction can be quite diverse and spread across many platforms. You might need to search on popular fanfiction websites like Archive of Our Own or FanFiction.net to find out.