When Kevin was a teenager, he ate like a horse.  This means that:

he didn't use a fork to eat.  He just put his face directly into his bowl.

Mary had to work like a dog to get good grades.  This means that:

she didn't work much and spent a lot of time sleeping.

she had to walk the teacher's dog for extra credit.

she had to participate in a dog-sled race to get extra credit.

Jenny has been a bookworm since she learned to read.  This means that:

My teacher told me to be as quiet as a mouse.  This means that:

I must make squeaking sounds like a mouse.

Marcus is as blind as a bat.  This means that:

We tried to tell Lucas that he needed to study more, but he was pigheaded.  This means that:

he wanted to spend time cooking bacon in the morning instead of studying.

When my boss said that it was time to talk turkey, she meant that:

we needed to be more polite to each other.

we needed to plan our Thanksgiving party.

Paul's younger brother James is a copycat.  This means that:

James likes to be different from other people.

When Kelly said that she smelled a rat, she meant that:

she believed that something was suspicious or dishonest.