Dee Dee thinks he’s too fat so he decides to go on a diet. Anything goes so he can lose a few kilos. And it works! He’s become so slim that he can walk right through the holes in Oggy’s roach swatter.Official Synopsis, 
One day in Oggy's house, he's chasing the roaches (as usual), who have stolen some of his food (and drink). Dee Dee then ends up eating all the food, causing him to slow down due to how fat he got. He then tries to fit into the vent, later helped by Joey and Marky, but to no success; as Oggy successfully has got the roach in the palm of his left hand. He then swats Dee Dee into a flattened, square-shaped insect; he only then proceeds to crawl away, like a worm.
In the vent, Joey and Marky then make fun of Dee Dee's fatness, much to his chagrin. When the roach does check his weight, he's apparently so heavy, he sinks into the ground and causes the scaler to break. Still unamused, he throws out all the food from the roach's fridge and replaces it with a single vegetable; as he starts to go on a diet. He proceeding orders a treadmill (which makes his brothers laugh at him again) and when it gets delivered, Oggy gets confused; until he notices Dee Dee, who came into the scene and then starts running on it. The cat then messes around with the speed by changing it repeatedly, until the roach couldn't even run on it properly anymore, and get launched to the vent, causing his brothers to again, laugh at him.
Later, Dee Dee decides to steal Oggy's steamy cooker, and then gets in; Joey activates it with the "cooked chicken" heat setting. Dee Dee starts to feel hot, and Joey proceeds to turn it up to the maximum ("sandal" heat setting), causing the pot to explode, which ends up getting him shaped into a ravioli. He walks away, awkward. Next, he proceeds to put all circular, flat objects on him, under the assumption that when he activates it, he will get himself reshaped into a skinnier roach. It actually ends up getting him electrocuted instead.
Now the roaches are eating. Dee Dee's only meal he served himself is the one vegetable from the fridge.
- Dee Dee manages to drink some soda from a bottle, despite the cap still staying on.
- Both of Joey's eyes are shown to be pink in the scene, where they watch Dee Dee getting swatted.
- In one scene, a skinny Dee Dee has Joey's colors.
- ↑ Oggy and the Cockroaches - Dee Dee’s Diet (S04E04) Full Episode in HD (published by OGGY on Jan 6, 2015, on YouTube. Accessed Mar 30th, 2019.)