Zetton is a beetle-like Kaiju that first appeared in the final episode of the series Ultraman. First appearing in the series as the bioweapon invasion monster of the Zetton aliens, Zetton is considered to be the most powerful monster in the original Ultraman series, and made many future appearances. However, more powerful Kaiju have appeared since then, though numerous stronger forms of Zetton have also been introduced throughout the course of the series as well.

After the SSSP thwarted Alien Zettons' evil plot, their HQ suffered severe damage in the process due to the Zettonian's alien vessels. Adding to the Science Patrol's difficulties, one of the aliens infiltrates the headquarters and subdues Doctor Iwamoto. The Alien Zetton then shapeshifts to disguise itself as Doctor Iwamoto, knocks out SSSP team member Akiko Fuji, and sabotages much of the Science Patrol's communication equipment and scientific instruments. The SSSP eventually chases down the alien and Shin Hayata shoots it in the head with his Mars 133 gun and kills it. However, before dying, the alien manages to utter the word "Zetton". Doctor Iwamoto and Fuji manage to recover.