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.
Well, perhaps there's a villain in the Loud House universe who has a connection to the world of Totally Spies. The spies - Sam, Clover, and Alex - come to Royal Woods to investigate. They meet the Loud family and realize that some of the Loud kids have skills that can assist them. Like, Luna's music skills could be used to disrupt the villain's mind - control device. And they work together, with the Loud kids learning some spy tricks along the way and the spies getting a taste of the Loud family chaos.
A possible plot could be that a WOOHP experiment goes wrong and creates a portal between the Totally Spies world and the Loud House world. Some of the villains from the Totally Spies side escape through the portal and start causing trouble in Royal Woods. The Loud family, being the resourceful bunch they are, team up with the Totally Spies girls. Lincoln could use his strategic thinking, similar to how the spies plan their missions. The sisters and the spies combine their forces, using their different abilities like the spies' martial arts skills and the Loud sisters' various hobbies and talents to defeat the villains and close the portal.
Chapter 104, "Camp Strength, Rapid Enhancement (2-in-1 Large Chapter)", is the clearest early answer because it turns Iron Ore's situation into a concrete plot event. The chapter turns that into something concrete by moving from Opening the camp system interface and seeing the data on Wood, Coal,... to Wood, of course, is not a problem, but 5000 units of iron mean even....
Chapter 79, "Luo Ming's Mouth Shines Brightly", is the clearest early answer because it turns Redwood Ridge's situation into a concrete plot event. The chapter gives readers a real answer by opening on The distance between Great Xia and Rogel Camp is actually just four... and ending on For safety, Xia Hong shortened the length of the team as much as....
Chapter 131, "The Entire Hunting Team Breaks Through", is the clearest early answer because it turns Deceitful Monster's situation into a concrete plot event. Early on, The panic brought by the Deceitful Monster visibly spread throughout.... By the end, The door opened, and Xia Chuan entered with a smile on his face,....
Chapter 149, "Supreme Combat Body, The Dangerous Gao Yu【Please Vote】", is the clearest early answer because it turns Twin Dragon Mountain's situation into a concrete plot event. The chapter gives readers a real answer by opening on Considering Great Xia's current activity area, a Cold Resistance... and ending on This person's fleeing was still being hunted by an Intermediate....
Chapter 142, "%, The Boiling Brought by the Martial Arts Training Ground [8000 Major Chapter Subscription Request]", is the clearest early answer because a shaky connection becomes usable in the plot. Early on, And those coming for the first time began to cultivate by imitation,.... By the end, It should only take one more day to finish them up." Xia Hong nodded,....
Chapter 77, "Luo Ming's Commission", is the clearest early answer because it turns Brother Xia Hong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Leader Luo, what brings you here?" It was none other than Luo Ming... and follows through with The entire cave sunk into silence..
Chapter 105, "New Home Construction, Strength Bottleneck [Two in One]", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter gives readers a real answer by opening on Except for these few kinds, only the Cold Beasts are currently the... and ending on In the past six months, Xia Hong has refrained from increasing any....
Chapter 94, "Building a New Wooden House", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. Early on, As the Cold Beast Meat was distributed, everyone couldn't wait to.... By the end, Calculating two jin per person per day, they wouldn't consume much....
Chapter 139, "Resource Gap, Changes in the Camp [Three-in-One]", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Leader, is it difficult to break through to the Cold Resistance... and follows through with Fortunately, Xia Chuan was now familiar with the camp's buildings'....
Chapter 105, "New Home Construction, Strength Bottleneck [Two in One]", is the clearest early answer because it turns Mu Dong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with When the new house construction idea was first proposed, Mu Dong... and follows through with Currently known human threats are limited to the camps of Lu Shang....