- Sergeant Keroro
- Private Second Class Tamama (silhouette)
- Corporal Giroro (silhouette)
- Sergeant Major Kururu (silhouette)
- Lance Corporal Dororo (silhouette)
- Hinata Fuyuki
- Hinata Natsumi
- Hinata Aki (debut)
- Space Leech (Male; debut)
The episode shows Keroro tied up, as Fuyuki and Natsumi head to school. However, Keroro manages to escape and decides to plot his revenge. Later on Natsumi and Fuyuki return home, both are worried about Keroro.
Natsumi, seeing Fuyuki's fear, offers to check the house first. Natsumi sneaks inside the house, but gets caught, as does Fuyuki. Natsumi and Fuyuki get confronted by Keroro, who explains where he came from. (Fuyuki and Natsumi appear surprised at his rank and name.) Keroro than brings out a space leech and is about to attack when Aki appears home. Fuyuki and Natsumi try to stop her from entering. However, Aki assumes they brought home an animal and ignores their warning. Aki opens the door to see Keroro, Keroro is unfazed by Aki's presence and actually tries to attack her. Only for it to backfire on him, however instead of the worst, Aki decides to keep Keroro, much to Fuyuki's excitement and Natsumi's dismay.
- In the original, Fuyuki took the Kero Ball, while in Keroro he didn't. This is the main difference.
- Mutsumi made a cameo in the original.
- Natsumi walked home by herself in the original, while both her and Fuyuki walk home together in Keroro.
- In the original Natsumi was stopped by a rope, but in Keroro both her and Fuyuki get ambushed by Nyoro.
- In the original Aki grabs Keroro, in Keroro it has Aki karate chop him.
- In Keroro, Aki doesn't mention wanting Keroro for her new Manga, while in the original she does.
- Also in the original Fuyuki mentioned having a parakeet, which is left out in the flash series.
- Yayoi and Satsuki, two of Natsumi's childhood friends, don't appear in Keroro at all.
- The episode is a tribute to what happened in the first episode of season one.
- In the original, Fuyuki mentioned how much his mother hated animals, and despite the parakeet scene not being added Aki still shows signs of hating animals.
- The star on Keroro's hat is missing during the romance scene.