A Half - Life 2 crossover with Mass Effect could be really cool. The advanced races in Mass Effect could get involved in the fight against the Combine. For example, Shepard and his crew could land on Earth during the Combine occupation and help Freeman. They could share their military strategies and advanced weaponry knowledge. Or a crossover with BioShock. Rapture could exist in the same universe as Half - Life 2, and the plasmid - using splicers could have an interesting interaction with the Combine and the resistance in Half - Life 2.
One idea could be a crossover with Portal. You could have Gordon Freeman stumble upon Aperture Science facilities. Maybe he teams up with Chell to fight off Combine forces that have also invaded Aperture. Another idea is a crossover with Fallout. Picture the post - apocalyptic world of Fallout combined with the sci - fi horror of Half - Life 2. Freeman could be in search of a way to stop the Combine using some of the unique technology from the Fallout universe.
In half life crossover fanfic, a great concept is the melding of Half - Life's science - fiction elements with those of other sci - fi works. This could involve the technology in Half - Life, like the HEV suit, being used in a new and different way when combined with the technology from another franchise. Also, the idea of different alien species from Half - Life and another series interacting can be really engaging. It allows for exploration of new relationships and conflicts.
One interesting plot idea could be Alyx and Gordon teaming up to explore a hidden area in the Combine - controlled city. They discover an ancient technology that could potentially turn the tide against the Combine. Another could be a story where Alyx gets trapped in a virtual reality created by the Combine and Gordon has to enter it to save her. Maybe a plot where they find a group of survivors with a unique ability and they have to protect them from the Combine's attacks.
One idea could be to crossover with another animated movie like 'Coco'. The characters from 'The Book of Life' could visit the Land of the Dead in 'Coco' and have adventures there. They might learn new things about their own afterlife concepts. Another idea is to crossover with a fairytale world. For example, having the characters from 'The Book of Life' enter the world of 'Beauty and the Beast' and interact with the enchanted characters. This could lead to some really unique character dynamics and story twists.
One interesting idea could be a crossover with "Moana". Elsa's ice powers and Moana's connection to the ocean could create a really cool dynamic. Maybe Elsa accidentally freezes part of Moana's ocean and they have to work together to fix it. Another could be with "Tangled". Rapunzel's long hair and her adventurous spirit combined with Elsa and Anna's journey in Frozen 2 would be exciting. Rapunzel could use her hair to help them climb mountains or cross chasms. A third idea is a crossover with "Beauty and the Beast". Belle's love for books and knowledge could help Elsa understand more about her powers and the history of magic in the Frozen world.
One idea could be to cross it over with a popular RPG world. The characters from 'No Game No Life' could enter a world full of quests, magic spells, and different races like elves and dwarves. They would use their gaming skills to navigate this new world.
One idea could be exploring Natsu's struggle to control his half - dragon powers. Maybe he accidentally causes destruction in the town and has to deal with the guilt and the fear of others. Another could be a story where Natsu discovers a hidden dragon clan related to his half - dragon heritage and has to prove himself to them.
One idea could be to explore what would happen if Charlie had a long - lost daughter who suddenly showed up. It would bring a whole new dynamic to the house and relationships. Another could be to write a story where Alan finally finds true love outside of the crazy situations he usually gets into on the show. Maybe he meets a woman at a book club who shares his interests.
One idea could be that Naruto discovers his half - angel half - devil heritage during a dangerous mission. Maybe he starts to have new powers like the ability to heal rapidly (angel side) and also to unleash dark energy (devil side) which he has to learn to control.
One plot idea could be that Naruto discovers his half - angel and half - vampire nature during a dangerous mission. His angel side gives him the ability to heal quickly and have a moral compass that is super strong. The vampire side, on the other hand, gives him enhanced strength and speed at night. Maybe he has to hide this from his friends at first because he's afraid they'll reject him. Another idea is that there's an ancient prophecy about a being like him who will save the ninja world from a new, unknown threat that is related to both the angelic and vampiric realms.
One idea could be that the half - slayer half - vampire struggles with their dual nature. They might have moments of extreme strength from the slayer side, but then be tempted by the vampire's bloodlust. For example, they could be in a fight against a powerful demon and find that their vampire side gives them an unexpected advantage, like enhanced speed, but they also have to fight the urge to feed on the demon's blood. Another plot could involve them trying to find a way to fully embrace both sides or choose one over the other. Maybe they meet other hybrids and form a group to protect the world in a different way than traditional slayers do.