Pinky and the Brain: Mice of the Jungle (1997)

The Brain's letter writing scheme is stolen by a brilliant but evil laboratory hamster named Snowball. He tries everything, but The Brain can't stop Snowball from taking over the world, which leaves poor Pinky stuck as the mouse in the middle. Then can Pinky and The Brain learn to live like wild animals, or will they lose their survival struggle in the great outdoors? When they're set free in the wilderness Brain's scientific knowledge is useless. But when the lord of the jungle turns out to be their old enemy Snowball, The Brain changes tactics quicker than Pinky can say, "Narf!"