The alien creature in “The Corbomite Maneuver” is named Balok.
Balok is introduced as the commander of the enormous Fesarius, the flagship of the First Federation. At first, the Enterprise crew sees a frightening blue-faced figure who threatens to destroy them after they enter First Federation territory and destroy a rotating cube that functions as a boundary marker.
Captain Kirk counters the threat with a bluff: he claims that the Enterprise contains corbomite, a fictional substance that would destroy any attacker. The apparent Balok then demands proof and sends a small tug to tow the Enterprise away. Kirk eventually turns the situation around by exploiting the tug’s limitations and boarding the disabled vessel.
The terrifying figure is revealed to be an effigy rather than the real creature. Balok is actually a small, childlike alien played by seven-year-old Clint Howard, with the voice supplied by Walker Edmiston. He explains that the encounter was a test of the Enterprise crew’s intentions and offers an opportunity for cultural exchange.