Sgt. Frog Episode 4 English Dubbed >Giroro suspects that the reason behind Keroro's lost interest in the Pekoponian invasion comes from a difference in humidity between Earth and Keron. He and Tamama install humidifiers in Keroro's room, which drastically increases his intelligence and strength, but the room becomes overly humid when it begins to rain, causing Keroro to go berserk. The humidity attracts a Nyororo, a natural enemy of the Keronians, which feeds on all the moisture Keroro had absorbed and returns him to normal.