What is the significance of the two imaginary visitors that Lennie sees while sitting on the river bank ?

Emphasizing the delusional nature of Lennie's point-of-view, Steinbeck adapts his one experimental narrative gesture in the novel, choosing to depict two hallucinations - first Aunt Clara, and then (more ludicrous still) a giant sardonic rabbit. It is unclear whether we are supposed to understand these hallucinations to be one-time phenomena or regularly recurring. (By the way, the reader may find it a bit unbelievable that this gentle giant, who everywhere else proves incapable of understanding figurative language, is able to imaginatively generate such colorful self-chastisements as "you ain't worth a greased jack-pin to ram you into hell" (112).)

Either way, Chapter Six represents our closest approach to Lennie's experience - his simultaneous fear and love of authority figures, his relentless obsession with the rabbits, and his constant (if confused) regret that he never fails to act in a confused and problematic way. Lennie, social pack animal that he is, has a deep-seated need for discipline and forgiveness. His self-chastisement is quite moving, both because it reveals a degree of self-understanding in Lennie and because it suggests that he is regularly and brutally upset with himself. His remorse hardly counts as a conscience - at no point does he register that he has committed murder, only that he has done yet another inscrutable "bad thing" - but it makes a claim on the reader's sympathy nevertheless.

His Aunt Clara appears to "yell" at him for the many ways in which he has "messed up" recently. This tells us something about the way his whole life has been lived. Then, a giant rabbit appears. The giant rabbit also emphasizes that George will probably treat him badly, showing us again how Lennie has lived his whole life being picked on by others and always being the butt of someone's anger.