The Goblin Gun can make people into goblins. It first appeared in episode 43 when Keroro wanted Kururu to use it on Natsumi Hinata to make her into a goblin, as revenge for her throwing soy beans at him. After making her into a Goblin, Keroro and Tamama (Anime Only) start throwing soy beans and other products at her. In the end Giroro, who is revealed to have been turned into a goblin himself, saves Natsumi from Keroro and Tamama, and thanks to Fuyuki Hinata, it turned out Natsumi was a Thunder God (Hence the Taiko Drums surounding Natsumi). Karara has also used it when she and Taruru (Chiroro in the manga) decided to try and invade Pekopon.