Ratchet & Clank: Up Your Arsenal Cheats

Go to Metropolis and follow the path over and into the first building, then hop up onto the left window sill and break the window, then hop across to the next building. Hop up onto the left side again and break this window, and there's a teleporter. Go to it at 3:00am-4:00am for the Insomniac Mueseum.

At Holostar Studios the second room that is raining (not the graveyard) there is a circular button to your right that will change it from raining to snowing.

If you collect all the trophies, the door in the trophy room will open up, revealing the Insomniac Museum.