They are immobile organisms that consist of a snaking worm-like body with a lure reminiscent of an anglerfish, connected to the ceiling by a barnacle-like base, which has a large, cat-like eye with orange, spike-like growths above it. They are encountered in various areas throughout the Cryosphere, such as the Sector Generator Room, and they are initially invulnerable to all of Samus's weapons, as they appear to possess an energy shield. Once she has obtained more upgrades like the Wave Beam, Super Missile, Screw Attack, or Power Bomb, Fumbleyes can easily be killed as these weapons are strong enough to penetrate and/or destroy their barrier. They use their tentacles to entrap Samus and serve as dangerous obstacles in the first part of the game.
"Fumbleyes will firmly grasp Samus with their tentacles and toss her if she gets too close. All weapons acquired after and including the Wave Beam, such as the Super Missile, Screw Attack, and Power Bomb are effective counters."
- A Fumbleye's characteristic eye is shared by a variety of organisms, including Phantoon (which also appears in Other M). Whether this suggests a relation or not is unknown.
- An organism resembling the Fumbleye appears on the Planet Zebes: Brinstar stage in the Super Smash Bros. series. Like the Fumbleye, it has a "tail" and is attached to the ceiling. However, it does not appear to have an eye and lacks many of the Fumbleye's features.
- The name of this creature is likely the portmanteau of the words "fumble" and "eye."