In Game:

A Katamari is the main object of the game.  The objective of the game is to roll the Katamari and collect items that miraculously stick to it to “send things to space” to create stars/planets.  It is typically a multicolored ball with large dull spikes stiking out of it.  It has the ability to pick up anything that is smaller than it and can charge at items with quick speeds and can even jump in newer versions of the game. 


The King of all Cosmos is literally the king of the universe.  He is basically the catalyst of the whole Katamari story line.  As the game play progresses the player gets more familiar with the life of the King and understands his story through vignettes that the player earns by defeating certain levels. 


The Prince is one of the main characters.  He is the son of the King of all Cosmos who is forced to literally clean up after his father and help repair the cosmos. 


The Cousins are other ancillary charcters in the Katamari Franchise.  In total, there are 58 playable cousins when all of the different Katamari Franchise games are added together.  In the original Katamari Damacy game there are only 24.  See below:

Gameplay: While in-game there are several items on the screen that the player needs to pay attention to in order to complete the level successfully.  These include the timer and the size indicator (in the upper right and left corner of the screen, respectively).  They are indicated on the following image:

Also, the character of which you are playing is shown in the bottom right hand corner of the screen typically indicating what you are doing at that moment.  For instance, if you make your character run while pushing the Katamari, the image would portray a rather hardworking prince/cousin pushing while running.  Also, the character will change depending on the level/area of the stage you are in.  For instance, if you run into the ocean to pick up under-water sea creatures, the character will don a snorkeling mask and flippers.  This is just one other way the Katamari franchise is detailed in its efforts to have fun!

Another cute aspect of the screen is the lower left hand object indicator.  This indicator tells the player what they just picked up in the Katamari.  The game is so detailed that you can literally watch/read every object that you have picked up in the Katamari, these can range from something as small as a pencil to entire buildings and even gods!