Up Your Arsenal is the first in the series to offer online multiplayer as well as single-player. Multiplayer features three different modes of play available on all of the maps and has a selection of the weapons from the single-player game. As well as the multiplayer mode, it offers many other improvements over its predecessors such as higher quality graphics, larger worlds and a larger variety of weapons and gadgets also ships and dune buggies . The voice cast from the previous game return as their respective characters and new actors have been hired to voice the new characters.
Despite straying further from a classic platform game, Ratchet & Clank: Up Your Arsenal still offers some of the basic features of a platform game but with a strong mix of action and shooting; PGNx Media has dubbed it a "combat-platformer". It offers melee and long range combat and boasts a large, varied arsenal as one of its primary features as it has been in previous games. Ratchet is initially armed with a wrench, his primary melee weapon, but as the player progresses through the game new weapons and upgrades can be obtained. As well as the 20 weapons available to the player, each weapon (apart from the RY3NO) has five levels of strength and then three after that once the game has been completed and the player starts "challenge mode". Alongside the weapons, which are primarily used for offensive/defensive purposes, there are ten gadgets that can be collected. They can give Ratchet the ability to run faster, jump higher or to solve specific puzzles.
For most of the game the player will be in control of Ratchet but in select areas the player can take control of Clank, Ratchet's best friend. Clank can give commands to smaller robots (similar to himself) called gadgebots to perform tasks with the use of a command menu to solve puzzles and attack enemies. The player usually takes control of Clank when there are no accessible routes for Ratchet, for example, when there is a route that only something of Clank's size could access. Clank also features in "Giant Clank" scenarios where Clank transforms into a larger form and can battle similar size enemies; in this form he gains increased fire power and a large amount of health.
During single-player gameplay the player is introduced to a 2D side-scrolling minigame (the "Qwark Vid Comic") where the player takes control of Captain Qwark and plays through his history in the Ratchet & Clank universe. Each vid comic contains numerous collectibles and collecting them all rewards the player with prizes such as skill points and titanium bolts and money(bolts). The vid comics are an integral part to the gameplay as their completion is required for the player to advance.
The game offers a huge range of enemies and different stages. Some enemies are found throughout the game but as the player progresses; they become stronger or take on new forms to provide more of a challenge.
Captain Qwark who was Ratchet's enemy in the second game returns with his own mini side-scrolling game. He leads the Q-Force and now is an ally. Sasha is the captain of the Starship Phoenix which acts as a base for Ratchet and the Q-Force. She is the daughter of the Galactic President and develops as a romantic interest for Ratchet. Dr. Nefarious, the antagonist of the game (voiced by Armin Shimerman), is the robotic form of a former organic life form. Ironically, he has a hatred for organic life and tries to destroy it. He has a history with Captain Qwark; it is mentioned that they went to the same high school and that Nefarious was bullied by Qwark. At the end, Doctor Nefarious is left stranded on an asteroid. None of the games from Deadlocked to Tools of Destruction for the PS3 featured him (Despite cameos and mentions), However he is seen at the end Quest For Booty, being the capture of clank and the leader of the Zoni.
Channel surfing past Clank's new TV show, "Secret Agent Clank" (a spoof of James Bond), Ratchet and his robot companion Clank stumble across a news report about his home planet, Veldin, which is under attack by an army of aliens named Tyhrranoids. The lead suspect is a mysterious villain by the name of Dr. Nefarious. After racing to Veldin and being mistaken for the new sergeant for the Galactic Rangers, Ratchet and Clank are contacted by the President on the whereabouts of the only man who has ever defeated Nefarious. It turns out it was Captain Qwark, who apparently lost his memory while working to save the Florana Jungle's fauna. He now believes himself to be a monkey. After Qwark and his companion Scrunch (a one-eyed monkey) are led to the ship, they are contacted by Captain Sasha of the Starship Phoenix, has been ordered to assist Ratchet and Clank.
The "Q-Force" (Al, Helga, Skidd, Ratchet, Clank, Qwark, and Sasha) is assigned a new mission to infiltrate Nefarious' base on Planet Aquatos to acquire as much information on Nefarious' plans as possible. They find that Dr. Nefarious is Clank's biggest fan, along with an encrypted star-map to the Tyhrranoids' home planet and base, Tyhrranosis. Nefarious and his butler Lawrence are shocked to see that their base has been infiltrated, and later find out Qwark is behind it. After Al decrypts the starmap, and the group infiltrate the base on Tyhrranosis and destroy it, Dr. Nefarious sends the Q-Force a transmission, still shocked that they actually infiltrated his base and Al traces the transmission to planet Daxx.
Ratchet and Clank arrive at Daxx and learn about the Biobliterator, but it is unknown of what it does for now. Also they find an edited Courtney Gears(a robot-like Britney Spears) Music video with a subliminal message to robots in it, fight the organic lifeforms. The story can head in one of two ways here, one path is to the Obani Moons. Where Ratchet and Clank check up about a transport from Planet Daxx to find out about the Biobliterator. However, access to the last moon, the Obani Draco, is unaccessible due to a "Omega class disintegration shield". Fellow Q-force member Skidd eventually shows up (after dealing with a "distraction", Clank asks if it was enemy robots, Skidd says it was the drivethrough at Galaxy Burger taking forever). Skidd then attempts to Hack into the Omega Shield while Ratchet and Clank help out the Galactic rangers at Blackwater City.
The other path is to follow up on Courtney Gears, first by winning the 'Meet Courtney' challenge at Annihilation Nation. Courtney will provide info on Dr. Nefarious whereabouts if Clank can get her a part on his show, Secret Agent Clank. Upon filming, Ratchet gets fired from his role in Secret Agent Clank after pushing the ejector seat by accident. Again. The rest of the filming turns out rather well, with Clank's new sidekick ironically being Scrunch. After shooting however, Courtney knocks out Clank and takes him to Dr. Nefarious. After Dr. Nefarious gives Clank the option to Rule the Universe with him, or be a disgrace to all robots by pairing with the organic life forms. The scene cuts back to Ratchet, and the Holostar Studios where Secret Agent Clank is shot is attacked by the Tyrranoids. Ratchet eventually meets up with Clank, but the player can tell something is up when Clank's eyes turn from green to red. With the filming complete and the Galactic Rangers safe, Skidd gets into trouble related to Courtney Gears after removing the shield on Obani Draco. Ratchet and Clank come to save him, but they are too late as he gets transformed into a robot. Courtney Gears attempts to do the same to Ratchet, but Ratchet defeats her in combat before she gets the chance. Sasha manages to track down Dr. Nefarious on a Star Cruiser called the Leviathan and Qwark is waiting for Ratchet at the Zeldrin Starport to infiltrate.
The Q-Force reaches the Leviathan and finds Nefarious waiting. It turns out that it was a trap, as he activates the self-destruct system and warps out. The Q-Force returns to the Phoenix, except for Qwark, who stays behind, claiming he thought he saw something. Ratchet and Clank fly off just as the Leviathan explodes, still debating whether to leave Qwark behind. Upon returning to the Phoenix, Sasha kisses Ratchet with joy that he made it out. After a funeral for Qwark on the Phoenix, Ratchet flies to the city of Metropolis, which is under attack by Tyhrranoids. During the battle, Nefarious uses the Biobliterator, a machine that turns organic life forms into robots, to turn helpless citizens and Tyhrranoid invaders alike into cybernetic creatures. The real Clank has been the prisoner of Doctor Nefarious ever since an evil copy known as Klunk replaced Clank and met with Ratchet at Holostar Studios. After defeating Klunk, Ratchet and Clank are reunited, and they fly to the planet Zeldrin to investigate the wreckage of the Leviathan. On Zeldrin, they discover that Qwark was alive when the cruiser went down but resolve not to tell the crew that Qwark is alive until they find out why he didn't report to the Phoenix. After discovering the whereabouts of Qwark's Hideout, they fly to the Thran Asteroid Belt to find Captain Qwark, who has abandoned his fight against Nefarious in favour of the comfort and safety of his hideout.
Ratchet and Clank reach Koros, and after battling hordes of Nefarious' troops, Clank uses the ion cannon there to destroy the Biobliterator. However, Sasha soon reports that a second Biobliterator is housed at a command center on planet Mylon, This Biobliterator is even more deadly and is guarded by an entire army of robot Tyhrranoids. Ratchet and Clank fly to Mylon, fight through the command center, and reach the Biobliterator, just in time to see Dr. Nefarious and Lawrence escape. A dropship arrives for Ratchet and Clank to pursue Nefarious to his launch site. At the launch site, Ratchet angers Nefarious, who attacks him. Though Nefarious is much tougher than he looks or acts, Ratchet defeats him. Nefarious and Lawrence then warp into the Biobliterator, which transforms into a giant robot. Captain Qwark flies in to fight alongside them and they engage in aerial combat against Nefarious and the Biobliterator and defeat it. The Biobliterator self-destructs, and Nefarious and Lawrence are left stranded on an asteroid after attempting to teleport away from the explosion. After Nefarious's defeat, Ratchet, Clank, and the Q-Force watch the premiere of the new Secret Agent Clank movie and Sasha gives Ratchet a kiss on the cheek.
Insomniac believe that one of the key processes in the development process was the rigorous testing. Working closely with Sony and listening to fans of the Ratchet and Clank series, they gathered feedback and made improvements to the game. They felt that they had created a game that would appeal to a number of genres with the inclusion of elements of platform, action and side-scrolling gameplay. At the same time, Jak 3 was being developed by Naughty Dog, a company closely tied with Insomniac. Naughty Dog's Jak & Daxter series and the Ratchet & Clank series are in similar genres; each game in both series' has been released at a similar time and both contain references to each other. Ryan Schneider, an employee of Insomniac, said, "The analogy that I like to use is that at Insomniac we like to look at it as how Tiger Woods and Michael Jordan and Kobe Bryant act when it comes to their professions. We don't really look at it as how we compare to other athletes or other games, we just try to do the best that we can and elevate the sport."
Before its release, IGN was highly anticipating the final version of the game as they had played two previous versions of the game already. Concentrating on the multiplayer aspect of the game they praised the developers for moving a solely platform game into the multiplayer genre so well. Ratchet & Clank: Up Your Arsenal was featured at the E3 games festival in 2004 and provided a playable demo to participants. Only "siege mode" and a single-player demo were available but they were enough to get 1UP.com's award for best action game at E3.
Soon after its release it received high praise from a number of game critics. GameSpy awarded it 5 stars out of 5; IGN gave it 9.6/10 saying that "You MUST buy this immediately" due to its extensive line-up of weaponry, high quality graphics and polished sound effects. IGN did however, believe it was easier than the previous game, Going Commando, where GameSpot thought that the gameplay was too similar to the previous title but both reviewers considered these as minor issues and they made little difference to the overall score. Gaming magazines Games TM and Official U.S. PlayStation Magazine both mentioned that the offbeat comedy that was apparent throughout the majority of the game was one of the points that made it unique. X-Play said "A mixture of excellent gameplay tweaks and new activities make the third one easily the strongest game in the series and one of the best games of this year" and giving it a full five star rating. According to Metacritic's collection of reviews, 12 separate reviewers gave the game the highest possible score. In 2006, Edge Magazine featured a “Time Extend” article on Ratchet & Clank: Up your Arsenal and among other points, focused on the amount and variety of weapons available to the player.
In August 2005 Up Your Arsenal entered the Greatest Hits line-up, reducing the price to $19.99. It has sold over 2.15 million copies in the US alone and has almost sold as many copies as the previous two games combined.