One interesting pairing could be Edward and Deadshot. Edward's ability to read minds could be really useful in helping Deadshot with his aiming. Deadshot, on the other hand, could teach Edward about human combat techniques that the vampires might not be familiar with.
Jacob and Killer Croc could be an interesting match - up. Jacob's werewolf strength and agility would be a good counterpoint to Killer Croc's brute force. They could start off as rivals, but as the story unfolds, they learn to respect each other's abilities and work together. Maybe they even develop a sort of friendship based on their shared love for a good fight and their loyalty to their respective groups.
Deadpool, without a doubt. His crazy antics, fourth - wall - breaking, and unpredictable nature would add a whole new level of chaos to the already volatile Suicide Squad. He would constantly be making jokes, getting into fights with the other members just for the fun of it, and finding unique ways to solve problems that the more traditional Squad members wouldn't think of.
Edward and Phoebe would be a fascinating pair. Edward's mind - reading ability and Phoebe's premonition power could lead to some intense and interesting interactions. They could also use their powers together to predict and prevent disasters in the crossover world.
Buffy and Carlisle would be an interesting pairing. Carlisle's calm and ethical approach to vampirism could contrast with Buffy's more action - oriented slaying. They could have deep discussions about the nature of good and evil in their respective worlds. Another interesting pair could be Willow and Alice. Willow's magic and Alice's precognition could lead to some really cool interactions and joint efforts to foresee and prevent threats.
I think Buffy and Edward would be a really interesting pairing. Buffy is used to dealing with vampires that are evil, and Edward is a 'good' vampire. Their interactions would be full of tension. Buffy might be skeptical of Edward at first, thinking he's hiding something more sinister. And Edward would be fascinated by Buffy's strength and courage, but also a bit intimidated by her no - nonsense attitude.
Eric Northman and Edward Cullen would be an interesting pairing. Eric is a bold and often ruthless vampire in True Blood, while Edward is more brooding and conflicted in Twilight. Their different personalities would create a lot of tension.
Another great pairing could be Jacob and Grover. Jacob is a werewolf with a strong sense of loyalty and Grover is a satyr, always looking out for demigods. They both have a connection to nature in different ways. Jacob with his wolf form and Grover with his love for the wild. They could have some really fun adventures together as they explore both the Twilight and Percy Jackson worlds.
Well, for me, Angel from 'Maximum Ride' and Alice from 'Twilight' would make a great pairing. Angel's psychic abilities and Alice's ability to see the future could lead to some really interesting interactions. They could work together to predict and prevent disasters in the crossover world. Also, Iggy from 'Maximum Ride' and Jasper from 'Twilight' could be an unexpected but cool pairing. Iggy's blindness and his other heightened senses might intrigue Jasper, who has his own unique vampiric abilities.
Ron Swanson and Jacob Black. Ron is all about his manly ways and love for meat and simplicity. Jacob, as a werewolf, also has a sense of masculinity. They could have a competition over who is more manly. Maybe they start a wood - working project together, but Ron is constantly annoyed by Jacob's werewolf - related absences when the moon is full.
One of the most intriguing combinations is Harley Quinn and Alice Cullen. Harley's chaotic and unpredictable nature paired with Alice's calm and prescient abilities would create a really interesting dynamic. They could either be at odds or find a strange kind of friendship. Another good combination is Deadshot and Edward Cullen. Deadshot's sharpshooting skills and his more jaded view of the world contrasted with Edward's brooding and his vampiric powers would make for some great scenes.