There are a lot of things out there that are difficult. I've always wondered if there is a way to quantify this difficulty. Luckily I've just managed to come up with a relational analogy system. Here's an example or three.
These types of analogies are best used in situations like the following; "You've got more chance of making it through an entire episode of Doctor Who than you do of sleeping with me." See how easy it is? If you find yourself in a position to say something like this then you are probably talking to some dork who knows what Doctor Who is. That makes the analogy so much sweeter.