Let's say a Halo Spartan and a Star Trek security officer team up. The Spartan could teach the security officer some new combat techniques, while the security officer could introduce the Spartan to the concept of diplomacy in the Star Trek universe. Their different perspectives would make for an interesting dynamic as they face various challenges together.
The characters could start off as enemies. For example, the Covenant leaders might view the Star Trek captains as heretics. But as the story progresses, they could find common ground in the face of a greater threat like the Borg or the Flood.
In a crossover, the Elites from Halo might interact with the Vulcans from Star Trek. The Elites' honor - based culture could be compared to the Vulcans' logic - based society. They could start off as adversaries, perhaps misunderstanding each other's motives, but then gradually come to respect one another as they learn more about their respective cultures and values.
The military - minded characters from Stargate, like Jack O'Neill, would likely be initially cautious and somewhat skeptical of the more diplomatic Starfleet officers. However, they would soon realize the value of Starfleet's knowledge and resources. On the other side, Starfleet officers might be intrigued by the Stargate technology which seems so different from their own. For example, Captain Kirk might be eager to explore through the Stargate.
One idea could be that the Covenant from Halo discovers the Federation in Star Trek. The different technologies and cultures would clash in really exciting ways. Maybe the Covenant would see the Federation's peaceful coexistence ideals as a threat to their religious beliefs.
In a fanfiction, Jaina Proudmoore could use her magic to study the energy shields of the Spartans. She might try to adapt that technology for use in Azeroth, perhaps creating new spells or enchantments. Meanwhile, the Spartans could learn from the mages about different forms of magic and how to use them in combat situations.
The logical Spock from Star Trek might be fascinated by the Transformers' mechanical nature and try to analyze them. Captain Kirk, on the other hand, would likely be more bold and adventurous in his interactions, perhaps even challenging the Autobots or Decepticons. Optimus Prime would probably see the Star Trek crew as potential allies in the fight for peace and justice, and he would approach them with respect. Megatron, of course, would see them as either threats or potential tools for his own evil plans.
The characters could interact through a portal that links their two worlds. For example, Master Chief could end up in Berk and be initially seen as a strange and powerful warrior by the Vikings. Hiccup, being the curious and open - minded character he is, would be the first to approach the Chief and try to communicate. They could then start to exchange ideas about their respective worlds and threats they face.
They could interact through combat. For example, the Spartans might fight alongside the SG teams against a common foe like the Covenant or a powerful Goa'uld army. The Spartans' combat skills and advanced armor would be a great asset in the Stargate universe battles.
The characters might initially be cautious of each other. For example, Shepard from Mass Effect could be skeptical of the Star Trek crew's non - violent approach at first. But as they get to know each other, they could start to share their skills. The Star Trek crew could teach Shepard about their advanced medical techniques, while Shepard could show them some combat maneuvers.
The Spartans from the Spirit of Fire would likely be very formal and military - like in their interactions. They might be a bit cautious around the more laid - back Star Fox crew at first. For example, they would greet each other in a very military protocol - based way. The Star Fox team, on the other hand, would be more friendly and open, trying to break the ice with the Spartans.
Sometimes, the interactions are based on a need for mutual assistance. A Star Trek ship might find itself in the Warhammer 40k universe and need the help of a local faction to repair their ship. In return, they offer their knowledge or technology. This can lead to some interesting exchanges as the characters from both universes try to understand each other's values and capabilities.