Cobalt

Cobalts are huge Blues who try to protect Big Blue by blocking oncoming Slush Fighters and forming a wall in front of him. They have the highest HP out of any standard non-boss enemy and block off anyone that gets too close to them through a stun effect. Your best bet at destroying them is to either attack them with someone invincible, or use range burst attacks.

Slush Invaders
Cobalts did not make a appearance in the movie. Instead the Limes got scrapped in the game for Cobalts.

Slush Invaders: Game
Cobalts will appear around the center of the screen and block off anyone who gets near them and cause a little damage. If left unattended, Cobalts will create a wall by standing on other Cobalts' shoulders, decreasing the player's chance of attacking Big Blue. Since their high health and ability to attack all fighters limit the ability to destroy them, the only way they can be destroyed safely is to either use range burst attacks or use an invincible fighter like Stomar. A fighter with Sticorey's invincibility boost can be used as an alternative to Stomar.

Another downside to facing a Cobalt is their ability to form a near impenetrable wall, made even more difficult if Azures were to come and cast shields over them, making taking them down even more of a challenge and frustration, especially if the Azures protecting them are behind their wall, making it almost impossible to destroy them and finish the level.

Strategy
Cobalts are defensive enemies who will attempt to form an impenetrable wall, to prevent the slush fighters from reaching Big Blue and other enemies. Despite not technically have a true attack, any melee fighter who attempts to attack a cobalt will suffer damage recoil, forcing them out of the screen. The only way for a cobalt to suffer damage is through the use of a ranged fighter (like Steric and Staddison) as, according to the game tips, this is the only true way to damage the cobalts.

However, it is also possible to use Stomar (who naturally becomes invincible upon beginning his combo), Sthang (who delivers a powerful phoenix attack upon receiving damage), Marcstick (with his evade upgrade which allows him to ignore seventy-five percent of any type of damage), Stucker (Automatically attacks anyone, just like Stomar), or a fighter protected by Sticorey’s invincibility shield (as they will be unhindered by the cobalt’s defensive shield altogether and directly attack anybody on the other side). If you don’t have the means to attack a cobalt but still want to get to Big Blue, try stunning the cobalt in question using Stedro’s blaster or Staddison’s stun grenades, then using Stick Dan to finish the Cobalts off. Stunning a Cobalt will confuse it for a moment, taking away their ability to use damage recoil.

The player may also use Stickwart's chain shots, increasing damage on the Cobalts making it easier to defeat one of them.

The best strategy is to get big blue high above the colbalt wall and use stick michael to keep big blue into the air above the colbalts.

Slush Tile Rush
Cobalts received a new design, with a different shield with a picture that represents their alliance with the blues. It was also revealed that they could talk. Their shields are more designed to look pretty. They have a defense of 5.

Trivia

 * Cobalts, along with Mobiles and Azures, are the only defensive enemies in the game.
 * "Cobalt" is also an element. See the periodic table of elements for much more details.
 * The Cobalts are basically just running shields with heads.
 * Cobalt shields can be found on racks throughout the Moon Prison level.
 * Cobalt is actually a shade of blue.
 * Cobalts, along with Azures, are considered one of the most annoying enemies in the game.
 * It is unknown if the Cobalts are robots or tall, large stick men.
 * Their shield could be counted as a hit when hit by Ultra Attack Blade Flurry.
 * The Cobalt is part of the new "Annoyance Rating" and is placed at the 3rd Spot, accumulating 87% Annoyance Rates.
 * Cobalts don't flinch to Stedro's "Blaster" upgrade.
 * Cobalts are hard to take down and has the highest HP for a minion.
 * Cobalts are annoying and almost unstoppable when they form a wall.
 * There are a number of fighters that can hit the walls and not get hit by the enemy. These includes Stucker, Stomar, Steric, and many others.
 * There is a Cobalt named "Cobalt the Third" at the very start of Slush Tile Rush.
 * In Slush Tile Rush in there shields design is noticeable the bolts are shown in the shield and you can see a picture of Big blue and two blues in the shield. The design also shows big blue holding blue paint, which is the paint he uses to convert regular people into blues.
 * A game-determined text that Cobalts can say is "Me block puny Slush Man. Again." This is a reference to what Cobalt the Third says when encountered.
 * This could also be a reference to the first game as the Cobalts' role was to block every Slush Fighters' attacks to defend Big Blue.