Ratchet and Jak was developed by both Naughty Dog and Insomniac Games. It takes place after Ratchet & Clank Future A Crack in Time. It was developed exclusively for the Playstation 3. It does no have to be considered canon.
The Plot Edit
It involves Ratchet and Clank accidently activating the Dimensionator which takes them into the Jak and Daxter universe. On arrival in Haven City, Ratchet lost all his guns and black market dealers have them.Then Jak and Dxater dicover them and there is a fight. The first boss battle. First you fight as normal Jak against Ratchet. When Ratchet loses, Jak turns into Dark Jak and Ratchet must fight him. The second boss battle. Then, Jak decides Ratchet is not bad. However, they are under attacks from the Metal Heads and the Dark Krimzon Guards. Also, an armada of robots is attacking. Ratchet cannot return, so he and Clank attack the Krimzon guard. Then Jak goes to fight the Metal Heads. However, after the Dark Krimzon Guard Commander reveals in the third boss, it soon turns out that the Dark Krimzon guards are lead by Gol and Maia who are attacking the world they also used the robots to invade. As a result Jak is now trying to fight more to find Gol and Maia, so Ratchet clears up the Metal Heads. Gol and Maia then reveal their plan: "If so many people attack Haven City, it will be so esperate with the Freedom Legaue gone that we can blackmail: If they don't give us the city, they will have no city to give us! They will obviously accept!£ Eventually, Gol and Maia are confronted by Jak who must fight Dark Makers. The fourth boss battle. Then Jak, about to be killed by Gol is saved by Ratchet. The fifth boss battle. It then ends with Ratchet finally grabbing the Dimensionator and leaving but Jak is accidently sucked in the wormhole and is now in Metropolis. Metropolis is under attack from Blargs who want to extract the city. Then Jak must destroy the Blarg and Ratchet helps and they are both confronted with Blarg Commanders. The sixth and seventh boss battles. Afer 10 more worlds of carnage for them both, It is discovered that Chairman Drek survived by teleporting away from the exploding planet.So, Ratchet is now obsessed with killing his enemy, while Jak has discovered some Cragmite armies lead by Tachyons' undead body. Ratchet fights him. The eight boss battle. Jak destroys the rest of the cramites while Ratchet destroys the blarg and then discovers they are on planet Orxon charging up the Obliterator which will blow up the galaxy. However, Drek reveals his evil plan: "Once the galaxies best planets are blown up, I will have revenge and also be able to make my new solar system and be so rich I can buy 5 galaxies, then do the same thing!". Ratchet then almost defeats drek, but then Drek get ratchet so Jak finishes him off. The final boss battles. or Dr. Nefarious is Reborn by Lawrence and Cyber Errol is back to they work together and take Revenge on Ratchet, Clank, Jak, and Daxter by gathering all the Villains they Defeated, by using time crystals he stole from the Great Clock.
A sequel has been revealed, which is the other way around (Ratchet style locations, then Jak) that will also include Sandover Village and Jak getting home. In the sequel Dr. Nefarious and Cyber-Errol return for their ultimate revenge.And the Agorians are back as well.
There is also a PSP spin-off developed by High Impact Games which is in between the two.
Ratchet: Constructo Pistol, Constructo Bomb Launcher, Construcor Carbine,   PIErociter- PIErocitator, Commando Rifle- Commando Killer, Constructo-Missile Launcher, Constructo Turret, RYNO X- RYNO XX, Zodiac 2: Peace Maker- Zodiac 2: Supernova, Jak: Blaster-Yellow Eco, Fireball blaster- Yellow Eco, Zapper-Yellow Eco, Vulcan Fury- Blue Eco, Laser Beam- Blue Eco, Rapid fire zapper- Blue Eco, Scatter Gun-Red Eco, Missile Gun- Red Eco, Eco Gravityt Bomb- Red eco, Peace Maker- Dark eco, Dark Ryno- Dark Eco, SuperNova- Dark Eco, Matter Rearanger- Dark Eco, Light Sheild Charger- Light Eco, Light Zapper- Light Eco,
The Gameplay is exactly like Ratchet and Clank when plaiyng as Ratchet and exactly like Jak and Daxter when playing as Jak like switching characters.   Secrets: If you USB link up to Jak and Daxter: The Lost Frontier you can unlock the following: The gunstaff and it's attachments to the Morph Gun. If you have Ratchet and Clank: A Crack in Time save you can unlock: RYN0 5,
Lava Gun, Miniturret glove Omniwrench Milllenium 14, Combuster and the Spiral of Death.
It recieved excellent reviews especially for not going too heavyily focused on one game and involving the action and explosions of them both. IGN rated it a 9.9 out of 10, and also recieved a 98% majority from other reviewers.