Complex sentence: Cooper even tries writing and jumps on the plate of liver to prove his identity as his mother knew that he liked liver very much, but fortune opposed them so Cooper and Fergie end up being switched with two chipmunks.
Split into simpler sentences: Cooper even tries jumping on a plate of liver to prove his identity; as his mother knows that he likes liver very much. But fortune opposes them and Cooper and Fergie end up being switched with two chipmunks.