Another option is a powerful sorceress. She could be using magic to create illusions and disrupt the order in both Gotham and the Totally Spies' world. Batman, who is used to dealing with more physical threats, and the Totally Spies, who are more into espionage, would have to learn about magic to stop her. Her motives could be to gain ultimate power by taking over the two different realms.
It could be the Joker. Imagine the Joker getting involved in a global scheme and teaming up with some international bad guys. His chaotic nature would be a huge challenge for both Batman and the Totally Spies. He would use his usual tricks like laughing gas and mind games, but on a much larger scale.
Perhaps a new villain, a tech - savvy criminal who has been observing both Batman and the Totally Spies. This villain wants to prove that he is superior to them both. He creates advanced gadgets and uses his intelligence to outwit them. He could be a former employee of Wayne Enterprises who was fired for unethical practices and now wants revenge on Batman and the world.
One possible plot is that a mad scientist creates a device that can manipulate time. This device falls into the wrong hands and starts causing chaos in both Gotham and the places where the Totally Spies operate. Batman and the spies get caught in the time - warped events. They have to figure out how to reverse the effects while also dealing with the changes in the timeline that are making their enemies stronger. The fanfic could explore how they adapt to these changes and use their unique abilities to save the day.
In a crossover with Danny Phantom, Danny would be a key character. His ghost - fighting abilities and the Totally Spies' skills in dealing with more earthly threats could combine in an interesting way. For example, they could face a villain who has the ability to phase between the ghost zone and the human world, and Danny and the spies would have to use their respective skills to stop him.
It could be Doctor Octopus. He might team up with some evil spy organization. His mechanical arms and scientific knowledge combined with the sneaky tactics of the spies would make for a formidable foe for Spiderman and the Totally Spies.
Dr. Octopus could be a great main antagonist. He could team up with a female super - villain from the Totally Spies universe. Together, they could create a plan to steal some top - secret technology. Dr. Octopus uses his mechanical arms to cause chaos in the city, while the female villain uses her own unique powers to keep the Totally Spies and Spider - Man at bay.
Obviously, the main characters from The Loud House like Lincoln, who could be the one to bridge the two worlds together. And from Totally Spies, Sam, Clover, and Alex. They would be the main characters as they are the core of the Totally Spies team. Maybe Lincoln's sisters like Luna and Luan could also play important roles, like helping the spies with their local knowledge or unique skills. For example, Luna could use her music to communicate secret messages or Luan could use her pranks to create distractions during a mission.
Sam, Clover, and Alex are the stars of Totally Spies. Sam has a great sense of logic and is good at analyzing situations. Clover brings the style and charm to the team, and she's not afraid to use her looks to her advantage during missions. Alex, on the other hand, is always ready for action and her enthusiasm often gives the team an extra boost.
One idea could be that the Totally Spies are sent on a mission to investigate some strange paranormal activities. They then discover Danny Phantom's world and team up with him to stop an evil force that is using both magic and technology to take over the world. Danny could teach them about the Ghost Zone and they could share their spy skills with Danny.
Danny would probably be in awe of the Totally Spies' high - tech equipment at first. He might try to figure out if he could use some of their tech to enhance his ghost - fighting abilities. Meanwhile, the spies would be intrigued by Danny's ghost powers. They could ask him to teach them how to turn invisible like he does. And Danny could learn some hand - to - hand combat skills from the spies.
In this fanfic, the setting could be a mysterious island. The Totally Spies are sent to investigate some strange energy readings. Meanwhile, Martin Mystery and his team are there looking into rumors of a cursed treasure. When they meet, there's some initial tension. However, as they start exploring the island further, they find that the strange energy is related to the cursed treasure. The Totally Spies' ability to hack into security systems and their combat training comes in handy, while Martin Mystery's ability to decipher ancient inscriptions and deal with the supernatural helps them understand the true nature of the curse. Together, they face off against a group of pirates who also want the treasure and the evil spirit that guards it.
One idea for a Spiderman and Totally Spies crossover fanfic could be that the Totally Spies are on a mission in New York. They accidentally stumble upon one of Spiderman's battles with a villain. Spiderman is initially suspicious of them but soon realizes they have the same goal of protecting the city. They then team up, with the Totally Spies using their high - tech gadgets and Spiderman his superpowers to take down the bad guys.