A rat in the grain is worth two in the woodpile.
The rat, huddled in his nest, plucks up courage and sallies forth.
A rat is just a mouse with an MBA.

A rat is a good judge of cheese.
The rat race is over. The rats won.
You can't teach an old dog new tricks, but you can teach a young rat anything.
A rat's god is cheese.
Life is like a rat race, but with more cheese.
A mouse in time saves nine.
The rat is the most maligned and misunderstood of all the world's creatures.
The best-laid plans of mice and men often go awry.
Even a blind squirrel finds a nut once in a while.

The early bird gets the worm, but the second mouse gets the cheese.

I've been called many things, but never a rat.
If you can't beat them, eat them.

The rat always knows when he is in the company of the cat.