While Lennie whines that he's always trying, Aunt Clara announces he never had any intention of leaving George the hell alone. Aunt Clara swears a surprising amount. Her grammar also leaves something to be desired.
Then, Aunt Clara disappears, only to be replaced by a very large and angry rabbit that (not surprisingly) also has Lennie's voice.
If you thought the dead aunt was bad, the scary, mind-reading rabbit reaches into Lennie and hits him where it hurts: it scoffs at Lennie's hope to tend to rabbits: he "ain't fit to lick the boots of no rabbit."
Lennie, rather than pointing out that rabbits don't tend to wear boots, just waits for more.
The rabbit suggests that George will beat Lennie with a stick and then leave Lennie: "He's gonna leave you, ya crazy bastard. He's gonna leave ya all alone."
As Lennie covers his ears in agony and cries out for George, the rabbit (according to the narrator) scuttles back into Lennie's brain, and George finally appears from the brush.