Thunderclap is a droid sent by Prizma to draw out Sailor Moon and Rini and destroy them. She can make thunder and lightning by banging on a drum, and even start a thunderstorm. She appeared in Sailor Moon R Episode 18, Trouble Comes Thundering Down.
After being told by Rubeus that Serena's greatest fear is thunder, Prizma sent Thunderclap to create a thunderstorm to draw out Sailor Moon and Rini. Once Rini used her power to make the gravity in a building disappear, Thunderclap was drawn to her energy and attacked her, but Sailor Moon came to stop her. Thunderclap used bolts of lightning to zap Sailor Moon, but her drum was broken by Tuxedo Mask, allowing Sailor Moon to destroy her with her scepter.
Thunderclap is the first droid whose task is not to take over a crystal point in Tokyo.