Castlevania is a world on which the main landmark is the eponymous, massive haunted castle. Simon Belmont hails from this world. The castle itself is home to all kinds of things that go bump in the night - vampires, zombies, werewolves, and many others - and the leader of this fiendish army is the most evil vampire of them all, the Count. The N Team has visited Castlevania on numerous adventures.
- "Mr. and Mrs. Mother Brain" - Simon shoots himself with a love arrow and falls in love with Mother Brain. While he goes off to Metroid with Mother Brain, the N Team is summoned to the castle (Kevin's first visit there) to deal with the Count and henchmen imprisoning the townspeople. Kevin, Lana and Duke eventually escape the Forest of Forgetfulness and Mega Man and Kid Icarus rescue Simon from the love arrow's spell. Simon defeats the Count and Mother Brain, her henchmen, and all the zombies are all banished.
- "The Most Dangerous Game Master" - Dr. Wily builds an android duplicate of Mike Vincent, a bully Kevin knew on Earth who used to be his friend. Mother Brain and company lure the N Team to Castlevania, where the android challenges Kevin to a race through the haunted halls of the castle. As Mike is about to finish Kevin off, Kevin manages to persuade him that he isn't all bad, and the two return to take out Mother Brain. When Mother Brain attacks the twosome, the android Mike is destroyed saving Kevin's life from the attack.
- "Metroid Sweet Metroid" - The world has a brief appearance here, in which Simon is seen celebrating his victory other Mother Brain and the forces of evil. He eventually breaks down and admits his story was exaggerated, but is captured by Eggplant Wizard and an army of vegetable monsters.
- "Simon the Ape-Man" - The Count is unleashing a horde of zombies to attack the world of Castlevania, but the N Team has its hands full since Simon has amnesia. Eventually the N Team ends up on Castlevania, and Simon, even stricken with amnesia, manages to ward off the Count and company.
- "Return to Castlevania" - Simon goes to Castlevania for an awards ceremony but is deemed a traitor by the person running the ceremony (who is actually the Count in disguise). Simon and Kevin fight through Castlevania, meeting Alucard, the Count's son, in the process. Eventually, Simon's good name is restored and the Count is put down for the count.