I believe you are right in your assessment of the prank. How I look at it is Neutrals do whats best for them whether its good for other people or not doesn't matter. Good people always strive for the betterment of others and evil strives for the destruction of others. Chaotic and Lawful are the means by which their goals are accomplished. Chaos is pretty much anything goes and Lawful will follow a plan and structure.

During my playtime I have found I dislike this system for making decisions. For example a lawful good may choose to execute a murderer if that was the law of the land but if the murderer in question was a kid then he might not be so quick to make the same decision. Some players make it a point to stick to their alignment and execute the kid anyway but I like playing with the fact that you do get to make the choice and it doesn't always have to be according to your alignment. It feels more realistic when a character doubts him/herself and maybe changes along the way based on the experiences they've had. Maybe a chaotic might learn from their lawful party members that structure is sometimes useful to further their goals. Maybe the lawful party member will learn from the chaotic one how to be more flexible. It's a good point of reference but I don't feel like it should be set in stone.

PS: Some DMs do reward you extra exp for sticking to your character beliefs and goals.