When all you can think about is rabbits and anything related to them.

An affectionate nickname for Nestlé Nesquik, which is a chocolate sauce that comes in a bottle resembling a bunny. When one turns the bottle upside down and squeezes it to get the sauce out, it appears as though the brains are being squished out of the bunny, hence "bunny brains".

n. insult. a person behaving especially belligerantly.