The following is a list of various characters in the fictional universe of the anime and manga series Sgt. Frog and related works.
The Keroro Platoon (ケロロ小隊 Keroro Shōtai) is led by Sergeant Keroro. While most platoons contain thirty or forty soldiers, the Keroro Platoon only has a meager five. Its full name is the Gamma Planetary System, the 58th Planet, Space Invasion Army Special Tactics Platoon (ガマ星雲 第58番惑星 宇宙侵攻軍特殊先行工作部隊 Gama Seiun Dai Gojūhachiban Wakusei Uchū Shinkōgun Tokushu Senkō Kōsaku Butai). In the English dub of the anime, the unit is referred to as the Advance Recon Mission Preparatory Invasion Terror Platoon (A.R.M.P.I.T.). Keroro refers to the acronym as being "unfortunate".
The initial operation of the Keroro Platoon was to stealthily survey Earth and relay information to the awaiting Keron Invasion Army. The five members were dispatched throughout Greater Tokyo and surrounding area to assess Earth's weakness and prepare for total military takeover. Having infiltrated the Hinata house, Sergeant Keroro concealed himself in one of the bedrooms, but was accidentally discovered by the Hinata children, a pair of middle school siblings. Shocked by their ability to see him, he was overpowered, captured and temporarily stripped of his weapon, the Kero Ball. With Keroro coming into direct contact with the Earthlings, the invading army lost their element of surprise, deemed the campaign compromised and immediately started withdrawal procedures from Earth's orbit.
Abandoned by the army and without the support of his platoon, Keroro must unite his scattered soldiers, survive his prisoner of war manual labor, and outwit his captors. He is eventually united with his platoon and subsequently given revised orders to continue the invasion campaign, but by themselves. Now, they must fulfill their new mission, protect their human friends, their home base, and the Earth from other alien invaders.
The platoon's hierarchy in military rank is similar to the Army ranks of the Japanese Empire during World War II and have based certain weapons, equipment and terms after the Imperial Japanese Military, but remains faithful to the perception of the alien invader with higher technological achievements.