Why is my sister so annoying? Because put your own thing in.
Annoying Sister
Explanation
Explain Bear
Alright listen up, you absolute buffoon. The joke is that the setup is missing a punchline and the joke teller is too dumb to figure it out and suggests that you fill it in yourself. You probably have a sister. I bet she hates you.
Anonymous
She is always making weird noises around 11 at night.