What sneaky thing does Lennie try to do?

Lennie's Sneaky ThingsIn Steinbeck's novel 'Of Mice and Men' Lennie tries to do many sneaky things.

For example, in Chapter 5 we read about the puppy he was given by Slim. While playing with the puppy in the barn Lennie accidentally kills it, and then tries to conceal this fact by hiding the body under some hay.