Fake Namek (偽ナメック星, Nise namekku-boshi) is a planet that only appears in a Dragon Ball Z filler. In the manga, Gohan, Krillin, and Bulma go straight to Planet Namek upon their departure from Earth. In the anime, however, the group encounters two obstacles. The first is an invisible spaceship full of children that mistake them for the henchmen of Frieza. The second is the fake Planet Namek.
The planet's disguised appearance has green sky and lakes like the real Namek, but also deserts, forests, caves, and castles. Its true appearance is a dark, cloudy area full of man-eating monsters. Raiti and Zaacro were trapped on the planet. A fog around the planet makes it inescapable unless the Stellar Winds are near.
Upon landing on the fake Namek, Gohan, Krillin, and Bulma are knocked unconscious. Raiti and Zaacro found them and took them into a building, creating illusions of a Planet Namek after reading their minds. However, it has not been explained why the false Namek appeared identical to the actual planet Namek before Gohan, Krillin, and Bulma crashed, and before Raiti and Zaacro had the chance to read their minds.
Raiti and Zaacro disguised themselves as Namekians and constructed some quests to find the Dragon Balls. The first Dragon Ball is found by Raiti under a boulder in the middle of a lake. The second is inside the mouth of a skull, in a coffin in an underground cave. The next three are more of a challenge: the third is taken by a monster dinosaur, who falls into a lake full of acid shortly after, forcing Gohan to go in with a specially designed suit, get the Dragon Ball, and escaping the lake with a Kamehameha.
The fourth Dragon Ball is inside a tornado, where Gohan jumps into it, grabs the Dragon Ball, and destroys the twister with a Masenko. The fifth is inside a giant's castle above a forest, where the forest floor comes to life in the form of tree birds that take Krillin, Gohan, Bulma, and Zaacro (who takes Raiti's place at this time) to the castle. The Dragon Ball is on the giant's earring, and the group get it off but, unfortunately, the giant wakes up. Krillin and Gohan fight the giant, causing some considerable damage to him, including one of the few instances where an enemy (albeit an illusionary one) suffers a direct hit from Krillin's Destructo Disk. Despite losing a hand, the giant is still able to fight back, until Bulma and Zaacro rescue Krillin and Gohan inside a toy airplane.
The sixth Dragon Ball is find frozen inside an ice cave. Krillin and Gohan slowly melt the ice with energy waves to get the Dragon Ball. When the cave begins to collapse (Raiti and Zaacro might be the true reason behind this), Krillin, Gohan, and Bulma sled down the tunnel on a block of ice. Raiti and Zaacro send a boulder after them, but the three manage escape the tunnel in time. The seventh Dragon Ball is inside a building, but man-eating sea monsters (who are not illusion) attack Gohan before he can get it. Raiti and Zaacro reveal their true forms and intentions, and the illusional building disappear. Bulma leaves to stall Raiti and Zaacro who intend to steal their ship, waiting until the Stellar Winds come so they can escape. Having dealt with the man-eating sea monsters, Krillin and Gohan stop Raiti and Zaacro just as they are inside the ship and knock them down. As the Stellar Winds are almost gone, Krillin, Gohan, and Bulma get into the ship. The group leaves the fake Namek through the Stellar Winds while Raiti and Zaacro are left on the planet.
Fake Namek can be explored in Dragon Ball Z II: Gekishin Freeza. Enemies encountered here are Nabana x2 or Krumbo and Navel.