Programming and 9/11

Listen up, buttercup. This joke is saying that both computer programming and the 9/11 attacks are "inside jobs." "Inside job" in computer programming means someone on the inside caused a problem. The joke implies that 9/11 was also orchestrated by people on the inside. It's funny 'cause, like, buildings don't usually fall down by themselves, and computer programs don't usually write themselves either. Also, you are definitely not smarter than the average bear.