Melllvar was a semi-omnipotent energy being who acted as the primary antagonist of the Futurama episode "Where No Fan Has Gone Before" - which parodied Star Trek and had Fry and the Planet Express Crew transported to an alien world where they teamed up with the actors of the original Star Trek series to escape the alien overlord.
Melllvar was a neurotic and obsessed individual who also had a great deal of rage, especially when Fry continually bested him in regards to knowledge on the Star Trek series: causing him to kill Welshy (a parody of Scotty) and continually fry his corpse in rage every time Fry outsmarts him.
He meets the Planet Express crew when they come to his world with Leonard Nemoy, revealing that he has watched all the episodes of Star Trek over and over ever since they came down to his planet, thus claiming himself to have an encyclopedic knowledge of the show, gathering the other members of the cast to his planet. Now with Nemoy among them, and the cast complete, Melllvar proceeds with his plan: opening a Star Trek convention that will last for eternity.
The convention eventually comes to Melllvar forcing the cast to perform his fan script. While they are rehearsing, the Planet Express crew attempt to escape, but decide to rescue the cast, only for them to fail and get pulled back down to the planet by Melllvar. Disappointed by the performance of the cast for his script and seeing how the Planet Express crew risked their lives to save them, he decides to pit the two groups in a battle to the death to see who is more worthy of his fanatical devotion. However, during the fighting, Melllvar's mother calls him for dinner and he is forced to leave.
With Melllvar temporarily gone, the cast and the crew combine the drive of the Enterprise to the Planet Express ship and escape... Only for Melllvar to pursue them in a mint condition space ship (which he was forced to take out of the package). It is here that Zapp Brannigan boards the Planet Express ship and begins a court martial, though an irritated Leela reminds him that Melllvar is still chasing after them. Just as Melllvar is about to destroy their ship, Fry reminds him that he can not let a TV show be his life and that he can do anything he wants. Melllvar agrees to end their chase and get a life, though not before he then boasts a condescending correction of knowledge at Fry about a Star Trek episode and then flying back to his planet as he laughs tauntingly.