Just mentioned this in another thread, it's my "favorite" of, uh...stuff I...yeah.
Take a magic academy that also happens to be near London, with a lot of anachronisms relating to a dissonance in campus policy and real life. Because the setting was once post-apocalyptic, fallout has turned the rain black and muddy (Note: This happens so often people assume it's normal), and one day while four girls are playing soccer there's some extremely heavy "rain" that causes the most timid of the bunch (I'll say person A) to decide now is the time to venture inside. Before that happens though, the sort of rough-and-tumble character (I'll say person B) points to a particularly large patch of mud in the grass and asks how far they think the other two can slide in it. Person A and her closest friend (I'll say C) quickly decline, but person B's best friend (D) says she thinks it's a wonderful idea, but tells person B to go first (Note: They use their shoes as markers). Person B has a go, only to end up tripping and falling on her face with a very wholesome splatter. Person D tries it herself, and easily passes her because she actually slid before losing momentum and falling. Person C then decides to try overtaking them all and actually succeeds. All eyes are on person A now, but she says she has no interest in getting dirtier than she is already. Person B says she intended not to get dirty and thus thought she could stop before she fell (Which of course is a flat-out lie) and claims person A can do that as well. Eventually person A agrees, and she manages to slide far enough to presumably overtake C if she were willing to accept a fall.