A very common type of introduction is the anecdotal introduction. This type of introduction uses a short story which represents the situation the writer wants you to have in mind when he presents the thesis statement. In this case, the story represents all similar situations which could happen to anyone with a dog. Taking the dog to vet serves a bridge to the explanation of the dog’s aggressive behavior.
Introductory Paragraphs - CommNet
anecdotal surprising statement ..
it is an introduction, not the paper ..