What if I open the box and let out the Schrodinger's cat and don't inform the experimenter?

you dont need to inform them

you became the experimenter when you opened the box (i.e you "collapsed" the wave function) and already know the result - the cat didnt die

 (The experiment ceased when the box was opened and you saw the result)

He'll figure it out when the litter box doesn't fill up any more.

When you open the box. You become the observer

The cat will be in a state of death or life after you observe it but before it will be both

You will have to buy him a new cat. 

You wont get any Milk

It depends on whether or not you, yourself are a sentient being.  I have my doubts.

It will run off toward a freeway, and you *still* won't know if he made it or not...

a) You can make friends with the cat 

b) You can take the liberty of feeding the cat 

c) You can leave the box open for physicists to contemplate 

d) You can have a heart-to-heart conversation with the cat 

and assure it that it is extant, and not just 'theoretical' 

e) All of the above (Not necessarily in the order listed)  

If you do this.....Quantum Physics will collapse!!

Seriously, you can’t figure that out? Duh.

Then the experimenter will be surprised when he/she opens the box to find nocat