When it turns out that the body in front of him is a fake, Nightwing growls and attempts to pull his head back out of the hole. However, because of the spike on the back of his head, he finds that he is stuck. He pulls back frantically a few times, but his head doesn't budge. This is bad, if he can't dislodge himself, he'll have to shrink down, and then it would be at least a minute until he can grow back - plenty of time for the rabbit to get the upper hand.