The guy-from-the-train phenomenon and creating delightful out-of-context surprises.
"A few tips for out-of-context user delights:
- Take an attribute that's normal and expected in one domain, and use it where it would not be expected.
- Take an attribute in your domain that's expected, and do the opposite.
- Bonus points if that opposite thing is also something that lets users off the hook (i.e. reduces guilt).
- Do something completely out of character.
- Combine two things that nobody would think to combine."
Full article: Creating Passionate Users blog.
