An audacious mouse gets into Oggy’s place and raids all the food. If there’s one thing that’s even more frightening for Oggy than the cockroaches, it’s A MOUSE! His only consolation, is that the mouse also takes it out on the cockroaches…
Official synopsis, 
The Outsider is the twentieth episode of Season 1 and was remade as the third episode for Season 6 under the title Cockroach vs Mouse. A mouse moves into Oggy's house and hassles the cat and cockroaches. This forces Oggy & The Cockroaches to team up to exterminate their pesky guest.
The episode starts with Oggy switching on the music to relax while cleaning the floor with a vacuum cleaner. When he push the drawer, he notice the wall which has been broken out by a neat freak Mouse. Noticing him, Oggy became frighten of him and jumps up to a tall drawer. The scene cuts to Stanley using perfume around.
The scene changes to cockroaches eating dirty food inside the rubbish bin. Mouse appeared again when he gets into the fridge. He smelled the cheese and add it with perfume. The cockroaches noticed the fridge filled with food feeling excited but ended up being hit by the fridge door when Stanley closed it.
When Mouse got out of the kitchen, Oggy appeared standing on the chair holding a hammer feeling frighten to slam on Mouse. Mouse then made a face, which caused Oggy to broke into pieces, then ran away from Mouse until he opened the door, which Mouse hit Oggy on with a big hammer.
The next moment, Oggy was still frightened with Mouse holding strawberries to eat. Joey walk to him and took a strawberry away from Mouse and point that it belongs to him. Angered, Mouse punched him and took the fruit back from an injured Joey.
That night, Oggy appeared hiding from a chair feeling scared and walk through walls until his bedroom. Better, he felt not worried and goes to bed. When picking up the blanket, he noticed Mouse sleeping, which caused him to be frightened again. He got out of the house and screamed, then came back to his bedroom. When Mouse woke up and saw Oggy stretching between walls and floors, he got out of the bed along with the pillow and went to the cockroaches' bedroom. He kicked the cockroaches out to sleep on their bed for now. The scene changed to Oggy sleeping, waking up when hearing snores inside. It reveals that the cockroaches were snoring on the bed when Oggy switch on the lamp. Joey then woke up and told Oggy to switch off the lamp, which Oggy relieved and switched off it.
The next day, the cockroaches gave Dee Dee in disguise as a woman. They gave him perfume to let Mouse smell Dee Dee and carried him. The plan is however failed, as he destroyed Dee Dee and get him out after kissing him.
The moment happened between Oggy sleeping on the pillow in the bathtub in the bathroom and Joey sitting on the toilet in the toilet room thinking, which they both had an idea. Joey and the cockroaches came in the room under the stairs holding a flower in which they get a poisoning ink with just on drop on it. Oggy then appeared holding a cake in which get the same ink with more poured on the cake. The scene changed to the living room where the cockroaches put the flowers on the vase on the coffee table and hide somewhere. Oggy appeared again putting the cake on the same table. He then saw the flower and smelt it, but caused to fainted due to the poisoning smell. The cockroaches noticed Oggy laying down on the floor, but were not amused about what happened. They then noticed the cake and ate them but also fainted.
Mouse suddenly appear laughing and sees in Joey's body and then the cockroaches. He sees Oggy's footwear and took it out, with bad smell, which caused him to fainted too.
The scene changed to the emergency room where Oggy and Mouse are on the bed and the cockroaches on the very small bed. Jack appeared holding a flower and a cake, which ends with Oggy and Mouse shocked and the cockroaches shivering.
- Oggy is a cat, and he is afraid of the mouse. However, in real life, the cats are supposed to chase the mouse.
- In this episode was written by Jean-Louis Capron no't Christophe Pittet, he supposed in storyboard, storyboarded by Christophe Pittet no't Jean-Louis Capron, he supposed in script.
- Oggy and the Cockroaches - The Outsiders (S01E20) Full Episode (published by OGGY on March 7, 2017, on YouTube. Accessed November 27, 2018.)