* A puppy's neck: He accidentally crushes the puppy's neck while petting it too hard.
* Curley's wife's neck: He accidentally breaks her neck while trying to stop her from screaming.
* A rabbit's neck: He accidentally breaks a rabbit's neck, which foreshadows his later actions.
* The bottle of ketchup: He accidentally knocks over a bottle of ketchup when trying to use it.
Lennie's strength and lack of control are a recurring theme in the story, and these broken items are a tragic reflection of his inability to control his power.