It is possible to have Hammy hold six Hamsterz for you -- five with Hammy and one out. Also, the more Hamsterz you have, the more you can go to the bedroom and get presents which lead to getting bigger cages faster.
Infinite (Unlimited) Stars
On Hamsterz 2 go to Uncle Mikes and zoom into the cage, stroke his hamster and you will see a row of stars. Zoom out again and zoom in again, and repeat the same process.