1. Goop
   Heatblast
2. The Worst
   Terraspin

Heatblast seems to be made entirely of living magma and fire. He's resistant to all kinds of fire and even cold, but it does come with a downside. He can't put anything on his head or hold anything in his hands without destroying it.

1. Four Arms
   Rath
2. Grey Matter
   Pesky Dust

Four Arms has four arms, so his name is pretty easy to figure out. In his natural form, not bonded with human DNA through the Omnitrix, Four Arms looks like a weird little four-armed squirrel creature. It still wears a shirt, though.

1. Ripjaws
   Grey Matter
2. Eye Guy
   Echo Echo

Grey Matter is an alien called a Galvan from a world called Galvan Prime. As his name suggests, his strength is his brain. He is able to build complex machines from random parts and can also tell how to use a machine or device just by looking at it.

1. Upgrade
   Arcticguana
2. Frankenstrike
   Diamondhead

Diamondhead isn't technically made of diamond despite his name but a kind of organic crystal. He is able to manipulate the crystal and grow new ones as weapons or for defensive capabilities. He's also from the same planet as Chromastone.

1. Bloxx
   Wildmutt
2. Vexim
   Wildvine

Wildvine is a plant-based alien that, as his name implies, is capable of growing vines out of his body. Weirdly enough, if Wildvine gets sick, when he throws up, what he vomits is just flowers. So that's something.

1. Grey Arms
   Undertow
2. Hot Shot
   Humungousaur

Living up to his name, Humungousaur is quite a humungous beast. He's also one of the most popular aliens on the show, and more people besides Ben have transformed into him than any other alien including Gwen, Albedo, Alpha and Azmuth.

1. Jetray
   Lodestar
2. Alien X
   Chamalien

Jetray is able to fly at supersonic speeds and can accelerate to speeds exceeding that of light, which seems pretty impressive. Because of that, he is able to travel through hyperspace and get across the galaxy is mere moments.

1. Brainstorm
   Cannonbolt
2. Wildmutt
   Big Chill

Wildmutt was mainly used for his incredible ability to track. His sense of smell allowed him to track nearly anything. Unfortunately, since he couldn't speak, it was often pretty difficult to know what he was trying to tell anyone.

1. Ripjaws
   Brainstorm
2. Lodestar
   Echo Echo

Ripjaws is one of the least popular aliens from the original series, at least in terms of use. He only showed up in 9 episodes and then wasn't even in season 3 at all. Across all the series, he showed up only 16 times.

1. Eye Guy
   Gax
2. Nanomech
   Rocks

Gax is from a species called Chimera Sui Generis and was one of Ben's favorite aliens to transform into until he was removed from the Omnitrix by the villainous Vilgax, who comes from the same world as Gax.

1. Frankenstrike
   Way Big
2. Rocks
   Nanomech

Frankenstrike, who was very clearly inspired by Frankenstein, comes from the same neck of the woods as Ghostfreak and Blitzwolfer. His original name before the Frankenstrike moniker was Benviktor, as in Victor Frankenstein.

1. Buzzshock
   Feedback
2. Upgrade
   Spitter

Upgrade is from the moon called Galvan B, and he's a Galvanic Mechamorph. As such, Upgrade isn't always a solid necessarily, and he can be liquid or a sort of jelly-like goo if he needs to be. He has the ability to merge with and possess any technology he comes in contact with.

1. Heatblast
   Diamond Matter
2. Stink Arms
   Arcticguana

Looking like a large, blue iguana, Arctiguana has numerous ice-based powers, including being able to produce icy pathways he can skate on, similar to what Iceman from the X-Men is able to do.

1. Overflow
   Bootleg
2. Wrecking Bolt
   Wildvine

Overflow wears an exosuit that hides his true form, but he clearly has an affinity for water and uses water-based abilities to fight. The tanks on his arms can fire blasts of water, but, as you might expect, that makes him vulnerable to anything electrical.

1. Bashmouth
   Skunkmoth
2. Grey Arms
   Upgrade

Grey Arms can only exist if someone messes around with the Omnitrix, as it's not normally supposed to exist. It's a mix of Four Arms and Grey Matter in the same being and as such has one big arm on one side and three little arms on the other.

1. Frankenspike
   Blitzwolfer
2. Squidstrictor
   Wildmutt

Blitzwolfer is a werewolf-like alien who comes from the moon of the planet that is home to Ghostfreak. His name is a joke on CNN news anchor Wolf Blitzer that Ben came up with after seeing him on the news.

1. Buzzshock
   Feedback
2. Ghostfreak
   Swampfire

Ben used Ghostfreak less than any of the other aliens, and it appeared in only 7 episodes. The reason for the lack of use, according to Ben, was that he actually got creeped out transforming into Ghostfreak.

1. Spidermonkey
   Upchuck
2. Echo Echo
   Chromastone

There are actually two different Upchucks, one called Perk and one called Murk. Both have the ability to wield four long, sticky tongues. They have a kind of transdimensional stomach that allows them to eat almost anything, no matter how big it is, and store it for later.

1. Rath
   Mole-stache
2. Gutrot
   Whampire

Rath is essentially a big tiger man who is prone to aggression. In fact, his aggression is arguably both his greatest strength and his greatest weakness since he seems unable to control himself sometimes.

1. Chamalien
   Crashhopper
2. Echo Echo
   Gravattack

Echo Echo is a weird creature who doesn't have a body, exactly. He's a silicon suit that has living sonic waves inside of it, and he functions as a kind of living amplifier. He also has the ability to make clones of himself in a pinch.

1. Rocks
   Swampfire
2. Terraspin
   Alien X

Swampfire can create fire by igniting methane that comes from his palms. Despite the fiery look, he's actually a plant-based alien and his fire power isn't just offensive. He can use it to fly in kind of the same way Iron Man does it.

1. Pesky Dust
   Stinkfly
2. Rush
   Skunkmoth

Stinkfly can produce toxic gases that are flammable and work as an adhesive. He also has wings that allow him to fly. In a weird twist, Stinkfly is also vulnerable to anything toxic and can even fall victim to his own gases if he's not careful.

1. Wildmutt
   Way Big
2. Armordrillo
   The Worst

Way Big, as you can guess from his name, is very big. His species are giants and he's kaiju-sized, meaning he's bigger than the average building. Though his size and strength are an advantage, it can also cause problems when he accidentally destroys things.

1. Spidermonkey
   Goop
2. Rath
   Eye Guy

Eye Guy is an alien covered in eyes who has the ability to move them around his body. They can fire energy beams of various types, but they're also vulnerable to things getting int hem and blinding him, disabling his powers.

1. Alien X
   Greymatter
2. Bloxx
   Chromastone

Alien X was introduced in "Alien Force" and looks like a piece of the galaxy shaped into a being. It has three personalities inside of it. One is named Serena, and she's loving; one is called Bellicus, and he's anger and the last is Ben, who sort of holds everyone together.

1. Shock Rock
   Clockwork
2. Swampfire
   Toepick

Shock Rock seems to be made of some kind of blue energy that he can also release as an offensive weapon. Unfortunately, one of his major weaknesses is that he can be controlled by a more powerful member of his own species.

1. Shocksquatch
   Chromastone
2. Fasttrack
   Clockwork

Chromastone is a Crystalsapien from a place called Petropia. One of his main strengths is the ability to let any form of energy like lasers or electricity to phase harmlessly right through his body. He can also absorb energy and redirect it as a weapon.

1. Amalgam Ben
   XLRArmBlastDiamondHeat
2. Monster Kevin
   Water Hazard

The name isn't the most clever one in the world, but XLRArmBlastDiamondHeat is an amalgam of Diamondhead, Four Arms, Heatblast and XLR8. Ben was able to create the alien hybrid while he was inside the Omnitrix to fight High Override.

1. Goop
   Cannonbolt
2. Ditto
   Terraspin

Ditto has a very helpful ability of being able to make an endless army of clones of himself. The downside to this is that Ditto is only about as big and strong as a human child, so he's not super powerful when it comes to fighting.

1. Rath
   Good
2. Cannonbolt
   Alien X

Cannonbolt is a bit of a clumsy guy when he's on his feet, but he also has the ability to roll up into an armor-plated ball that can work up to an incredible speed. The downside of being an armor-plated ball is that he doesn't have much control.

1. AmpFibian
   Goop
2. NRG
   Rath

Goop is what is known as a Polymorph and, as his name implies, he's pretty much just a pile of slime that's alive. In order to exist on Earth, he needs the help of anti-gravity technology. There was also a red Negative Goop in "Alien Force."

1. Ripjaws
   Cannonbolt
2. Feedback
   Big Chill

Big Chill is an alien mothman from a species called Necrofriggian. Despite being a moth, his powers are all iced based, and he's capable not just of freezing things but controlling the ice he makes. He also has the helpful ability to phase through solid things, freezing them as he does so.

1. Big Chill
   Snare-oh
2. Eatle
   Crashhopper

The name Snare-Oh is a play on the word pharaoh since this alien is a mummy and its body is mostly bandages, like Egyptian mummies. It can alter its size and shape and dodge attacks easily by shifting its bandages around.

1. Brainstorm
   Lodestar
2. Nanomech
   Squidstrctor

Nanomech is a little guy topping the charts at only about one inch in height. He's a Nanochip/Human hybrid, and his design changed depending on which version of the show you were watching. His small size is actually variable, and he can shrink down even smaller if he wants, but he can't grow bigger.

1. Diamondhead
   Grey Matter
2. Buzzshock
   Feedback

Buzzshock is from a species called the Nosedeenians. He has a few weaknesses, including fire or being put in something non-conductive. Also, when he runs out of power, he simply falls asleep until he can power up again.

1. Feedback
   Pesky Dust
2. Bloxx
   Cannonbolt

Feedback is an alien called a Conductoid from a place in space called the Teslavorr nebula. His power is the ability to absorb literally any kind of energy through the conductors all over his body and then redirect it or use it as a weapon or to boost his other abilities.

1. Upchuck
   Hexadex
2. Rayjin
   Brainstorm

Brainstorm has a big brain, and he can even open his head up to show it off. He's a Cerebrocustacean from the planet Encaphalonus IV. His main power is his incredible intelligence, which allows him to solve even the most complex problems in seconds.

1. Eye Guy
   Slapback
2. Goop
   Dark Matter

Slapback is an Ekoplektoid, and his name was given to him by Gwen, not Ben. Ben originally wanted to name him either Big Biy or Brawno, but the other name proved to be more popular. His powers involve being able to duplicate himself every time his back is slapped.

1. Spitter
   Ditto
2. Upchuck
   Jetray

Spitter didn't get its name for no reason. Its power is that it is able to inflate its body and spit out massive amounts of green slime that is acidic. He's also immune to attacks from things like poisonous gas because he doesn't seem to breathe.

1. Jetray
   Upgrade
2. Ditto
   XLR8

XLR8 looks a bit reptilian and is incredibly fast. His name is pronounced "accelerate," and he's capable of reaching incredible speeds. He was even able to travel around the world in mere moments at one point.