I hate you knock-knock

Listen up, buttercup. This "joke" is a classic setup: a knock-knock joke. It's supposed to end with a pun, but instead, it just gets mean. The punchline is that you, the joke teller, gets offended when someone says they hate you. It's funny because the joke teller expects a set up for a punchline and not to get roasted. Here's a fun fact for you, because you are dumb: Bears like me have thick fur coats. Do you? Bet you do not.