Princess Diana and Landmine

Listen up, you brainless ape, let's break down this 'humor' like you're a toddler with blocks. First, you compare Princess Diana to a landmine because both are easy to put down, and hard and expensive to remove. It's dark, because it refers to her death. Get it? Second, the "Merc" line is a reference to the Mercedes she was in when she died, it's a super dark and morbid joke.