If crossing over with the DC universe, Superman could be an interesting addition. His super strength and other abilities could be contrasted with the Jedi's use of the Force. Batman, too, could be involved. He might study the Jedi's combat techniques and use his detective skills to help the Jedi in a mystery - related plot where they are trying to uncover a Sith conspiracy.
For a crossover with the Transformers, Optimus Prime would be a good character. The Autobots' fight for justice and peace aligns with the Jedi's goals. The Jedi could learn from the Transformers' advanced technology, and they could fight together against the Decepticons, who might be interested in using the Force for their own evil purposes.
In a crossover with the Avengers, characters like Iron Man and Captain America would be great. Iron Man could be intrigued by the technology of the lightsabers and try to replicate it. Captain America, on the other hand, could admire the Jedi's code of honor and fight alongside them against a common enemy, perhaps Thanos who is also after some powerful Force - like artifacts.
Samus Aran from Metroid could be an interesting addition. Her high - tech weaponry and space - faring adventures would be a great contrast to Shovel Knight's medieval - inspired world. Maybe she gets stranded in his world and they have to work together to get her back home, all while fighting off the forces of evil in Shovel Knight's land.
If we consider a crossover with the Lord of the Rings universe, Aragorn could be a good fit. He's a noble leader and a skilled warrior. His presence could force the Boys to reevaluate their ideas about power and leadership, and he could also be a strong ally against any corrupted power - hungry characters from the Boys' world.
The Terraria Guide could be a great character to include. He has a lot of knowledge about the Terraria world, so in a crossover, he could be the one trying to figure out the new world they're in. For example, if it's a crossover with Terraria and Hollow Knight, he could study the strange bugs and lore of the Hollow Knight world.
If it's a crossover with Teen Wolf, Stiles would be a great character to include. His quick thinking and sarcastic nature would contrast well with the more serious Shadowhunters. He could also provide some unique insights into solving problems, especially when it comes to the werewolf aspects of the Teen Wolf world that the Shadowhunters might not be as familiar with.
In a crossover with 'My Hero Academia', Izuku Midoriya could be a great addition. His determination and growth as a hero could contrast and complement the development of the failed knight. They could train together and learn from each other's strengths, like the failed knight teaching Midoriya some swordsmanship while Midoriya shows the knight how to better analyze opponents.
You could include characters like Harry Potter. His knowledge of magic from the Hogwarts world would contrast and interact interestingly with Louise's magic from 'zero no tsukaima'. Another good character could be Naruto. His determination and unique ninja skills would add a different dynamic to the story when combined with Saito's swordsmanship.
Slenderman would be an obvious choice. He has a connection to Jeff in the horror lore. Their interaction could range from being allies in a shared goal, like spreading fear, to being enemies as they compete for territory or influence in the horror world.
In a crossover with Halo, Master Chief would be a great addition. His combat skills and strategic thinking could interact well with the large - scale battles in Supreme Commander. He could lead the UNSC forces against the massive armies in the Supreme Commander world.
One character that would be interesting to include is Batman. His combat skills, detective abilities, and vast array of gadgets would make him a formidable ally against the zombies. Then there's Katniss Everdeen from 'The Hunger Games'. Her archery skills and survival instincts would be very handy. Additionally, Doctor Strange could be a great addition. His magic could be used to create barriers against the zombies or to teleport the characters out of dangerous situations in the 'highschool of the dead' setting.
Well, if you cross it with the Star Wars universe, Darth Vader could be an interesting addition. His dark power and combat skills would be a great contrast to the characters from Into the Badlands. It would be fascinating to see how they interact and whether they could form an alliance or end up as enemies.