Free Weapons
Insert the memory card with your save file from the original Ratchet and Clank game, then start a new game. Ratchet will start with the five weapon that carried over from the last game, in his arsenal for free.
Random Stuff menu
The Random Stuff menu houses a few extras that will help show you your progress on the game. You unlock the menu by entering Challenge Mode. Once you do, you'll find it pre-loaded with a Space Invaders minigame, and a Paintings gallery. Once you gather all of the weapons, modifications and ship upgrades, you'll also unlock a video about Clank's day at Insomniac studios, as well as corporate sponsorship, in the Endorsement Deals.
Snow Skin
Enter the Impossible Challenge at the Arena, and complete all of the levels to unlock Ratchet's Snow Skin. The Snowman skin is a running joke in the game.
First Person Mode
The game is a third-person platform-adventure game, but if you prefer First Person perspective, this game does have a hidden mode. Play through the game once, and when you complete it, you'll find First Person Mode is now an option.
Skill Points
You collect skill points for doing certain things on certain planets: breaking anything that's breakable on Endako, fighting all of the enemies on Dobbo with only Ratchet and Clank 1 weapons, or finishing the Barlow hoverbike race in less than 1 minute and 45 seconds. The game contains an entire wealth of skill points, which you can check on the progress of on the Start Menu.
Big Head Modes
Bobble-heads play off the image of comically large craniums, and you can play with the characters' head sizes in this game, too. After you get five skill points, you can turn on Big Head Mode for Ratchet; 10 skill points for Clank. After 15 skill points, you can make the NPCs' heads humorously huge, and the same for enemies once you get 25 Skill Points
Ratchet Costumes
After you collect seven skill points, you can earn a touch of class with Ratchet's Tuxedo skin. After 20 skill points, you can put him into a Clown suit. Finally, 30 skill points unlocks the Beach Boy outfit.
Mirrored Levels
Once Ratchet's earned 12 different skill points, you can put the levels into Mirrored mode. The layout will be exactly the same, but reversed: where you would have turned left in standard mode, you now go right.