Ambassador Mervin is the antagonist of the Futurama episode "A Taste Of Freedom".
He is the Ambassador of Decapod 10, Zoidberg's home planet, to Earth. When Zoidberg ate the Earth's flag, he was chased by an angry crowd to the Decapod 10's embassy. After Zoidberg's Supreme court trial, in which he was sentenced to death, the army tried to seize the embassy to arrest Zoidberg. In revenge Mervin sent Decapod fighter ships to enslave Earth. During the battle, he sent Zoidberg to steal the codes for Earth's global defense system, which leaves Earth unable to fight off the invaders and lose the war. Mervin forced the humans to build The Mobile Oppression Palace, a massive robot which could be used to enforce their rule on Earth instead of costly fighter ships.
The Planet Express crew went to museum with weapons displays, hoping to find a weapon that wasn't shut down during the invasion. They find a heat seeking missile from the 20th century and fire it at the place, hoping to destroy it. But the missile could not hit it, as all Decapodian technology was cold-blooded.
Zoidberg then realized his mistake in enslaving Earth, particularly after Mervin callously crushes the lawyer who had previously defended him in his trial when the man acts defiant, and lit an Earth flag on fire and threw it at the Palace. This allowed the missile to find it's mark and blow it up, freeing the Earth and making Zoidberg a hero. It is unknown what happens to Mervin after the episode, but it may be possible that he returned to the job.