On their Wagon Train to the Stars, our intrepid heroes come across a planet with a single defining characteristic. Everybody is a Robot, or a gangster, or a Proud Warrior Race Guy, or wearing a hat. To some degree, this is unavoidable; you only have so much screen time or page space to develop and explore a culture. But it's still very easily and often overdone. For maximum typing, the characters can also be physically uniform, as in People of Hair Color. Bonus Points if a planet's Hat is one that requires a Nice Hat.
