Sidehopper

Sidehoppers (Side Hoppers in earlier media) are bipedal, insectoid enemies in the Metroid series, first appearing in Metroid.

Description
Sidehoppers are insectoid creatures whose hind legs have abnormally developed in comparison with its shrunken body. The majority of Sidehoppers are weaker than their evolved relatives from Norfair with the exception of the rare, blue variant found only in Tourian (vulnerable to nothing but Super Missiles). The common Sidehopper is as big as Samus and has a pair of powerful, piston-like legs enabling it to perform great leaps, and two enormous mandibles hanging directly beneath its head. Sidehoppers have the strange ability to repel gravity; they can not only cling to the ceiling, but also jump from it then "fall" upwards back onto it.

In their original incarnation in Metroid, Sidehoppers, like many enemies in the game, had two different forms: one pale orange with a green head, the other vermillion with a blue head. The vermillion ones were more resilient and powerful than their cousins. In Super Metroid, there were three variations of these creatures: Small Sidehoppers (most likely juveniles), normal-sized and the previously mentioned powerful, armored variant called Blue Sidehoppers.

In the remake Zero Mission, another further evolved creature related to the Sidehopper was introduced, the Baristute. These creatures were stronger than both the Dessgeega and Sidehopper species in the game.

This wildlife was also seen in Metroid Fusion, but these were either infected Sidehoppers from the Biologic Space Laboratories research station or imitations by the X Parasites. DNA modifications gave them thrusters at the bottom of each leg and added resistance to attacks. Another noticeable addition is their vicious look.

Metroid: Other M concept art reveals that the Sidehopper, Dessgeega and Baristute are an evolutionary line. It is unknown what triggers this evolution.

Metroid manual
"These powerful enemies attack Samus while hopping. Be careful, the Side Hopper's strength is second only to the Mini-Boss. Destroy him with one missile blast."

1986 manga
"This tough new enemy hops and jumps when attacking."

Official Nintendo Player's Guide
"It attacks Samus with a double-jump movement pattern."

Super Metroid manual
"Sidehoppers pounce on intruders with powerful legs."

Super Metroid Nintendo Player's Guide
"Because they bounce unpredictably, it's best to either shoot quickly or avoid them."

Combat
In the original game, Sidehoppers were very dangerous, the most powerful enemies in the Brinstar region, particularly the brown variety and the ones that walk on the ceiling. It is best to dispose of a Sidehopper with a blast from Samus' Missile Launcher or Screw Attack if available; to avoid confrontations, freeze them with the Ice Beam and flee.

Sidehoppers remain dangerous opponents in all their subsequent appearances, thus maximum firepower is advised. In Metroid Fusion, all Sidehopper-X are more armored than their normal counterparts, making them immune to uncharged beams. Sidehoppers are found in Sector 3 instead of Sector 2 where one would expect to find them.

In Other M they are capable of releasing a shockwave when they land from their jumps, increasing their attack range.

Cameos in the Prime series
In Metroid Prime, the Biohazard Containment room on the Frigate Orpheon contains a roaring inhabitant and a shaking door. Scanning the unit reveals images of a very Sidehopper-like creature, though no name is provided. The fate of this creature after the crash is mysterious, as its cell will later burst open with Aqua Reapers after passing through the area once before, which does not produce a body despite the door apparently remaining locked. The scan on the Frigate reads: "Specimen Solitary Holding 1. Phazon level >> Unknown. Status >> Xenotropic life-form unstable. Use caution." It being referred to as a xenotropic creature supports the theory it is a Sidehopper.

In Echoes, there is a multiplayer arena named "Sidehopper Station". Appropriately, it is also shaped like a Sidehopper. The stage is based on the Frigate Orpheon, and is likely a reference to the cameo in Prime.

Trivia

 * It is possible that the blue armored Sidehoppers are unnatural and possibly created from Space Pirate technology. The fact that they were only found in Tourian supports this theory.
 * It is interesting to note that while Sidehoppers are native to tropical areas, they are found in Sector 3, the desert/volcanic habitat on the BSL station. Additionally, Dessgeegas, who live in volcanic areas, are found instead in the tropical Sector 2 aboard the BSL station. The X Parasites are known to modify the abilities and DNA of their victims, which might explain this change of natural habitats.
 * In a pre-release trailer for Fusion, the Sidehoppers were depicted with a red coloring, making it match with its volcanic surroundings.
 * The head structure of Sidehoppers in Other M loosely resembles Phazon Metroids.
 * There is a glitch in Other M whereas if a Sidehopper is shot off a platform, the creature will walk back in mid-air as if it were still on the platform, only to fall when the animation is completed. The same applies to the Dessgeegas and the Baristutes.