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.
A possible plot could be that there is a threat to the world that involves both superpowers and high - tech espionage. The Totally Spies are called in to investigate the technological aspect, while Spiderman is already on the scene dealing with the super - powered part of the threat. They cross paths and at first are not sure if they can trust each other. But as the situation worsens, they realize they need to work together. They combine their unique skills, like Spiderman's web - slinging and the Totally Spies' ability to blend in and use advanced gadgets. In the end, they defeat the common enemy.
Well, perhaps a mad scientist creates a portal that connects the two universes of The Loud House and Totally Spies. The Totally Spies are lured into the portal and end up in Royal Woods. They meet the Loud family and soon realize that the same scientist is planning to use a powerful device in Royal Woods to control the minds of people all over the world. The Loud kids and the spies then form an alliance. The spies teach the Loud kids some basic self - defense and spy techniques, while the Loud kids show the spies how to blend in with the local community and use everyday objects as tools to stop the scientist.
One interesting plot could be that an ancient artifact has been stolen. The Totally Spies are on the case because it has some high - tech implications, while Martin Mystery is interested because it has a dark and mysterious past. They both follow different leads that eventually converge at an old, abandoned castle. There, they have to fight off various traps and enemies, both normal and supernatural, to get to the artifact and stop the villain who plans to use it to gain ultimate power.
One possible plot could be that the Totally Spies girls are on a mission to stop a new villain who has some high - tech gadgets. Spider - Man accidentally stumbles into their mission while chasing a petty criminal in the same area. At first, there's some confusion and mistrust between them, but they soon realize they can work together. The Totally Spies share their intelligence on the villain's lair and Spider - Man uses his super strength and web - slinging to help them infiltrate it.
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.
A crossover with Sailor Moon might also be cool. The Totally Spies could find themselves in the Sailor Moon universe and have to help the Sailor Scouts fight against a new enemy that is after some powerful artifact in both their worlds. The spies' espionage skills would be useful in gathering information about the enemy's plans, while the Sailor Scouts' magical powers could be used in direct combat.
One idea could be that the Loud sisters get recruited by WOOHP. Maybe Lincoln accidentally discovers a WOOHP gadget and the spies come to retrieve it. They notice the Loud sisters' unique skills and talents. For example, Lori's bossy nature could be useful for leading missions, and Leni's fashion sense could help with disguises. They all team up to stop a villain who is using a new technology to take over the world.
One great plot idea could be that the characters from Young Justice and Totally Spies are brought together by a common enemy. Maybe a powerful villain has a plan that affects both their worlds, like a device that can mind - control both superheroes and spies. So they have to combine their skills to stop it.
Perhaps in a fanfic, Todd has a secret that only Red discovers. This secret could be related to his past or some special power he has. Red helps him deal with it, and through this process, they grow closer. Their relationship could be a slow - burn one, starting from friendship and gradually evolving into something more romantic as they go through various adventures and solve spy - related problems.
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.