What does Lennie "see" in chapter 6?

Lennie sees the giant rabbit and Aunt Clara in Chapter Six.

And then from out of Lennie’s head there came a little fat old woman. She wore thick bull’s-eye glasses and she wore a huge gingham apron with pockets, and she was starched and clean. She stood in front of Lennie and put her hands on her hips, and she frowned disapprovingly at him.
And when she spoke, it was in Lennie’s voice. “I tol’ you an’ tol’ you,” she said. “I tol’ you, ‘Min’ George because he’s such a nice fella an’ good to you.’ But you don’t never take no care. You do bad things.” And Lennie answered her, “I tried, Aunt Clara, ma’am. I tried and tried. I couldn’t help it.”

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Aunt Clara was gone, and from out of Lennie’s head there came a gigantic rabbit. It sat on its haunches in front of him, and it waggled its ears and crinkled its nose at him.