The boss can be a cat, and you have to maul him

Cats smaller than dogs...

But yeah we can use a cat as a rival throughout the game

I really need to get some basic plot premise sorted out to decide what the bosses could be.

And you could befriend Mice and use them to confuse the cats!!! lol

a tiger!!!

YES and they are in the cat family

One of the missions could be to eliminate the tiger in the Zoo because he's controlling all the cats! Or something like that.

We could have stealth elements implemented in this level, or the dog could pretend to be a stray and try to "charm" all the guards at the zoo.

Then you could "summon" mice and a minigame could start where the mice go accross a 2D world to get into the Tiger's cage, into the tigers fur and inject him with poison!

It would be good if I can give other options to the player to eliminate the tiger. But if we go with the Mice thingy it won't really be a "boss battle"

... ???

I don't know how to call my game and I also don't know how it will work exactly, but I have at least the basics:

We all know that there are so many FPS games out there, especially games about World War II. My game would be set in WWII (could also be another war) as well, but you're not a soldier, you're a civilian who experiences all the evils of a war. Basically you have to survive, probably by hiding yourself and your family from the enemy soldiers, by providing/getting enough food and water, by escaping enemy troops, etc.

I don't how a game like this could be made engaging enough so that you want to go on with the story, but basically it's a good idea, I guess.

It could be that I read something like similar a few years ago somewhere in the internet, but I'm not sure, so I posted it.

Super Parking Extreme!!!!!!!!

You start the game as a valet driver at a high dollar hotel or casino.  The object is to park as many cars as possible to make the most money in a night.  As the game progresses many challenges are thrown in.  One will be having to park a car with a standard transmission and your character doesn't know how to drive one so the challenge is to hit buttons precisely so you can get the car into first gear.  Later, you have to drive after having a bad reaction to a medication (drunk driving) and the controls become unresponsive and slow to react.  By the end of the game your character is broke so he really needs to park a bunch of cars as fast as possible to pay bills.  The character will hit ramps and transfer is body weight to land in a single spot that is at first surrounded by no cars and eventually 2 cars.  You'll also be tasked with sneaking up on other valets and stealing their fairs.  Robbers will also be trying to thwart you so you'll have mini games where you open the door and knock them out or have to pull them out of a car they've already stolen.  Sometimes, the car will break down and you'll have to push it into the spot.  Flat tire?  The faster you change the tire, the more you level up so you can change a tire more quickly.  Ice roads, hurricane force winds, hail, and fog will also be included to add more challenge.  Motion controls may be added to make it more realistic and will be a PSN or XBLA game. 

Many more scenarios can be easily incorporated. 

A medieval fantasy RTS where fortresses with walls that you put units on similar to Battle for Middle Earth, only deeper- and realistic siege weapons play a huge role. There are boats in there too, and when there are ship battles, you not only need to control the boats, but the units on the boats weather you use your cannons, or board the enemy pirates of the carrabean style. And there would be dragons and fantasy beasts availible too all with unique mechanics to them.

Cutting edge graphics would be sacrificed in order to have huge epic armies duking it out.