Mellows are purple, red, and green flying creatures that are found in Brinstar in the original NES Metroid game, its remake and Super Metroid. In the NES and SNES game, they behave in the same manner as Mellas and Memus, in which they hover near a ceiling and swoop down quickly when Samus passes below them.
In the mentioned remake, Zero Mission, Mellows can only be found in a limited area of Brinstar (about 5-6 rooms) and disappear for the rest of the game if Samus Aran destroys all of their nests, one of which is hidden behind a wall blocking access to a Missile Tank. Mellows will defend their nests when a threat comes too close for comfort. Mellows spend most of their time circling their nest when the latter is found within the same room, or chasing foes when there is no nest nearby.
"These creatures can pass through walls. They like to chase after you in groups."
"Travels in groups through rocks and walls. These weak creatures are defeated in one shot."
"Small and weak but pesky, they will swoop down at you diagonally."
- The creatures known as Mellas and Himellas are possibly related to Mellows, given their similarity in name, behavior and physiology.
- Artwork in the Japanese strategy guide for Metroid: Other M implies that Mellas and Himellas are subspecies of Reo. This would subsequently make Mellows a subspecies of Reo as well, although they are not featured in the game.
- The Mellow hives seen in Zero Mission bear a strong resemblance to the Fly Pods featured in Other M. It is unknown if they are the same structures or not.