Don't believe your lying eyes. Really.

The giant bunny picture was a bit misleading. I saw videos of Herman, and he is not that huge -- merely very, very, very big for a rabbit. I think there is some forced perspective going on which resulted in the confusion. Notice how the farmer was holding his arms out at a funny angle to get the rabbit as close to the lens as possible.

For a less extreme, and unintentional, illustration of this principle at work, behold Ur-Dodo:

For the record, Dodo weighs about 17 pounds, give or take an avoirdupois, meaning she has the same mass as Herman.