Keroro Land

Keroro Land is a children's magazine that is focused on the anime and manga series Sgt. Frog. The magazines contain games, previews of future episodes, advertisements for merchandise, and even a section of yonkoma comics drawn by several well-known dōjinshi artists. The magazine also contains a section where children can send in drawings of their own Keronian creations and the winning entries are drawn by Mine Yoshizaki. Although it is unknown what the winning entries were going to be used for, a card game entitled "Anokoro Keroro Gunso" was created where some of the winning Keronian designs were used as characters. Some of these characters also made it into the Anime series.
The card game is a prequel that revolves around the original Keroro Platoon's first real mission. Keroro, Giroro, Zeroro, Firuru and Zoruru form their own teams and split up to fight the Black Stars, a team of four deadly dare devils bent on conquering Keron.