Keys

The black key is located in Pixel's house under the bed upstairs and is a "key to a door" in the basement.

The green key is located in a green house across the street form Pixel's house behind the radioactive barrels upstairs and is a "key to the sewers".

The red key is located in the red house's shed in the toolbox and is a "key to a roof door" on the top of the red house.

The white key is located in the "UFO" under some rubble and is a "key to a machine" at end of the 2nd town with all the shops.

The yellow key is located in "Duckywow's Duck Shop" behind a duck on a shelf behind the counter and is a "key to a door" in the duck shop.

The bronze key is located in the red house which you can grab it from the broken window and is a "key to a floor door" inside the red house once you get in through the roof door.

I know there are other keys, but i don't know where they are. If you know where they are, please edit the page.