A cybernetically-enhanced Sidehopper, this creature has four legs as opposed to a regular Sidehopper's two. Therefore, it is presumably not a natural specimen. There is only one known Doublehopper, and it is located in Brinstar.
Samus Aran encounters the Doublehopper at Room A-22, which is divided into three sub-chambers separated by shutter doors. After first defeating or escaping from a normal Sidehopper in the first chamber, Samus can continue into the second chamber containing the Doublehopper. The Doublehopper acts as the second guardian of Kraid, the Mini-Boss who resides in the third chamber, and therefore must be defeated before Samus can confront Kraid.
The Doublehopper has two attacks, which it uses in retaliation when Samus misses an attack. The first is a normal jump attack that deals 5 damage (3 with the Varia equipped). The second is a large jump that deals 10 damage (8 with the Varia equipped).
Samus can use the Ice Beam, Wave Beam, or Missiles to fight the Doublehopper, with each weapon providing unique story segments. The Power Beam, Bombs, or Screw Attack will not damage the Doublehopper. If Samus does not have any weapons to fight the Doublehopper, the Command Computer will recommend a retreat to Room A-20. However, there is a low chance that Samus will fail to escape and the Doublehopper crushes her with a single 10-meter-high jump attack; the Doublehopper continues to jump in triumph as Samus dies.
The Wave Beam always has the greatest chance of hitting the Doublehopper. If Samus misses the first hit, the Doublehopper retaliates with a weak attack. If Samus misses the second hit, the Doublehopper retaliates with two strong attacks. It takes two successful shots of the Wave Beam to kill the Doublehopper.
The Ice Beam only has a low chance of hitting the Doublehopper the first time, although its accuracy improves after landing the first hit due to the ice slowing down the quick Doublehopper. If Samus misses either shot, the Doublehopper will only retaliate with weak attacks. It takes two successful shots of the Ice Beam to kill the Doublehopper.
Missiles are the safest option, since they are guaranteed to instantly kill the Doublehopper without Samus taking any damage. Missiles have about 50% accuracy against the Doublehopper, so it only takes five missiles if Samus does not miss, but it can take up to ten missiles if Samus misses her shots. If Samus does not meet the required number of missiles, the attack will still be successful but will consume all of her ammo. Since Kraid can only be damaged by missiles, Samus should be wary of her ammo and may need to retreat if she does not have enough missiles.
The Doublehopper does not drop energy or missiles when defeated.
"Doublehopper. An evolved Sidehopper with additional modifications. This cyborg creature guards the area immediately outside Kraid’s Room."