The Jupiter King is a giant defensive robot created by the Rebel Army to guard their secret factory. It is heavily armored to protect the nuclear reactor inside the robot's body. The lightly-armored head (which resembles a toy robot's head) serves as the robot's weak point.
Its armaments consist of a missile pod on its left arm that allows the robot to fire several homing missiles. Its prehensile right arm is equipped with a large claw-like manipulator that can be changed to destroy the surface in front of it. The robot's eyes are also capable of emitting lasers to attack enemies. The Jupiter King also has a "belly button" that can create a large missile, from which the robot grabs and plunges into the surface.
The battle with Jupiter King takes place in an infinite stretch of room with a pool of molten metal underneath the surface. In battle, the Jupiter King continually moves to the right, while it attacks by firing a series of homing missiles, firing a delayed but deadly laser from its eyes, and change its pincer claw to destroy the surface. After taking a certain amount of damage, the Jupiter King will use a new attack; launching a large missile from its "belly button" and grabbing it with its pincer claw, then crashing it into the surface, destroying a portion of it and producing multiple fireballs to fly over the player.
The player can earn weapons by shooting at the flashing homing missiles.
In Other Games
The Jupiter King is a playable unit available for purchase once stage 10 of World 2 is beaten. Despite the Jupiter King having a high AP cost (at 900 AP), its only attack is firing lasers with a long delay. A mini version with the same attack pattern is available.
To compensate with its reduced attack kit, a variant called the Jupiter King MK II was introduced. It has the same AP cost and cooldown time as the original one but its stats are way better than those of the standard Jupiter King (i.e. Jupiter King has 15,000 HP at level 30 with Jupiter King MK II having 40,000). It attacks by dropping missiles.
The Jupiter King is a playable unit as part of the "Metal Slug Defense x Battle Cats" collaboration event. An Uber Rare Cat, the Jupiter King only has its laser eyes as its attack, although it can knockback enemy units and slow down Aliens.
RPG! Sister Quest
The Jupiter King appears as an enemy as part of the Metal Slug crossover event.
The Jupiter King is available as a Super Rare unit. Its attacks has been improved to launch missiles, drop missiles, and fire lasers. The mini variant and MKII return, and new variants and redesigns are introduced.
Army Men Strike
Jupiter King appeared in the Metal Slug 3 collaboration event.
Upgrades and Variants
|Jupiter King: The original version.|
|Jupiter King MK II: An improved version of Jupiter King with some graphical changes: Its red accents are now purple (including the missiles and its inner head) and its pincer claw now moves forward and backward all the time. This version seems to have lost it's eye lasers, but it's possible that it just prefers not to use it. It is also a lot better armored than the original one. Appears in Metal Slug Defense and Metal Slug Attack.|
|Jupiter Queen: Another variant the Jupiter King, this time made by the Ptolemaic Army. It is colored in pink and silver/white. It also uses its eye laser for its normal attack and its Pyro-Arm for its special attack. Appears in Metal Slug Attack.|
|Golden Jupiter: As it name implies, it is a golden version of Jupiter King. It uses the pyro arm and the laser. Now both attacks produces deadly fireballs to damage the enemies, and if it is attacking, it won't be destroyed until the animation ends. Unlike it's predecessors, the "lightning" created before using the laser can also damage units it touches.|
|Mini Jupiter King: A mini version of the Jupiter King. First appears in Metal Slug Defense as a special reward for 20 million downloads. It has the same features but lower attributes. It returns in Metal Slug Attack as an obtainable unit through the Medal/V.I.P. Crank, combining the special attack of its original variant as a long range attacker and the Special Attack of the MK II.|
|JQ-032mini: A mini version of the Jupiter Queen controlled by Caroline.|
|Mini Jupiter King MK II: A mini version of Jupiter King MK II. It's stronger than the original Mini Jupiter King, and can use its laser, as opposed to its "giant" counterpart. Similar to Golden JK, the "lightning" deals damage to units it touches.|
|Sky Jupiter King: A flying version of Jupiter King. It's tracks and arms were replaced accordingly with rockets and empty sockets. It can launch pods known as "Jupiter King Heads" and can also launch missiles.|
|Sky Jupiter Queen: A version of the Sky King built by Caroline during her captivity in the Rebel Army. Like its Ptolemaic ground-based counterpart, it copies the special attack of its Rebel version (and as such, launches missiles). The eyes can also be adjusted to shoot out lasers at enemies.|
|Sky Jupiter Queen MK II: A version of the Sky Queen modified for use by Ptolemaios' cultists, with the eye beams now modified to engulf the targeted area in flames.|
|Jupiter King Head: A small pod-like heads piloted by Rebel Infantries which are summoned by the Sky Jupiter King. They fire energy balls as their regular attacks and they can crash towards enemy forces as suicide attack.|
|Perfect Jupiter King: An ultimate weapon developed by the Rebel Army. It has a much more robotic features than its predecessors, hence being true to its name. It is piloted by both Donald Morden and Allen O'Neil and attacks with its powerful stomp and fists. When the lower body is destroyed, Allen will attempt to lift the upper body with his superhuman strength, essentially acting as the robot's limbs. In this form, the Perfect Jupiter King now resorts to powerful melee punches, while using its double arm cannons and laser eye as a special attack.|
|Jupiter Tank: A giant artillery weapon developed by the Rebel Army retrofitted for more mobility and firepower. It runs on tank treads, its arms have been replaced with energy blasters, and it has two fire cannons on its shoulders.|
|Jupiter King (Kai): A new model of Jupiter King built by both the Rebel Army and the Ptolemaic Army to protect the laboratory and factory facilities in their alliance. Unlike the previous Jupiter King models, this version attacks with energy spheres, energy pillars and fire deadly lasers from its mechanical arms.|
- This boss, as the entire third mission, is a reference to the Metal Gear series by Konami.
- The background of the boss arena is a redraw of the Hairbuster Riberts' arena in Mission 2 of Metal Slug: Super Vehicle-001.
- When the Jupiter King is destroyed, there is a chance that its head color will appear bronze instead of silver.