In a crossover with a more fantasy - based world, a character like a wise old wizard could be paired with Caboose. The wizard could initially be frustrated by Caboose's lack of understanding of the new world's magic and customs, but over time, they could form an unlikely friendship. Caboose could teach the wizard about loyalty and friendship in his own simple way, while the wizard could teach Caboose some magic tricks.
Most likely, the caboose itself is a main character. Since it's about the caboose's strength, it's going to be central to the story.
It could be the leader of the red team. Maybe he gives the caboose the toughest and most dangerous tasks without any proper recognition.
Maybe the Caboose could cross over into a world where the rules of combat are completely different. His Red vs Blue training would be put to the test, and he'd have to adapt quickly. For example, instead of using guns, they use magic or some other form of power. The Caboose might initially be confused but then find his own way to contribute.
Sasuke and Tex might be likely to be paired up. Both are strong and somewhat brooding characters. Sasuke's quest for power could be paralleled with Tex's own abilities and her role in the Red vs Blue universe. They might engage in some intense battles or even end up having to work together against a common enemy, leading to some interesting character development for both of them.
In this fanfiction, the caboose could get angry if it has a goal or a dream that is constantly being thwarted by the red vs blue conflict. Let's say the caboose wants to bring peace between the two sides but they keep ignoring its efforts. It tries to communicate but they just laugh at it or don't take it seriously. So all these rejections and lack of respect make it angry.
In this 'caboose's wedding red vs blue fanfic', Caboose is the central character for obvious reasons. Then, considering the nature of Red vs Blue, characters like Tex might also be involved. Tex has had a complex relationship with the other characters in the series. Also, the leaders of the Red and Blue teams could be main characters. They might be responsible for security during the wedding or for making sure everything goes according to plan in their own bumbling ways.
Well, it really depends on the size of the fan community. Red vs Blue has a decent following, and if the fanfiction manages to capture the essence of both the Caboose character and the Freelancer concept in an interesting way, it could be fairly popular within that niche. But overall, in the grand scheme of all fanfiction out there, it may not be as well - known as some of the more mass - market ones.
One popular fanfiction might be 'The Adventures of Caboose and Carolina'. It could focus on their teamwork and how they overcome challenges together in the Red vs Blue universe. Maybe it shows Caboose's innocent yet powerful nature interacting with Carolina's more serious and skilled persona.
Well, one interesting aspect could be the unique character development of the caboose. Maybe it shows how the caboose's strength is portrayed in different scenarios, like in battles or challenges within the 'Red vs Blue' universe.
Definitely Church. He has such a complex personality and backstory that it would be interesting to see how he interacts with characters from other crossovers. His snarky comments and leadership (sort of) qualities can add a lot to the story.