Modest Royalty/Playing With

Basic Trope: Members of the royal family dress in everyday, functional clothing.

Straight: Prince Bob of the Kingdom of Tropevania, wears plain shirts and otherwise normal clothing most of the time, and will change into formal garb only under duress.
Exaggerated: Prince Bob wears t-shirts and shorts on all occasions, even extremely formal ones.
Justified: The attitude in the kingdom is against grand display, and Bob dresses down to sway with this notion.
- Prince Bob played with some commoner children as a kid, which influenced his less than regal behavior.
Inverted: Bob wears his Requisite Royal Regalia on all occasions, even barbecues, sporting events, and pool parties.
Subverted: Bob appears to wear very simple clothing, but it's made of silks and velvets and is probably more expensive and lush than jewels and fur capes.
- Alternatively, Bob wears a mere loincloth--it's his body he's showing off.
Double Subverted: He was kidding when he said that.
Parodied: Bob looks like a monk.
Deconstructed: Bob dresses plainly because no one, not even him, takes his title seriously. The monarchy is a complete joke and the ruler is just a figurehead. Consequently, when he is called upon to lead in a crisis, no one will listen to him.
Reconstructed: Bob dresses plainly because he is not only a pretty face but a competent leader, and he doesn't need showy clothes to command respect.
Zig Zagged: Some royals wear ornate clothes, others dress more casually. Bob's mother is likewise sensible with her outfit but his sister wears too much jewelry to move.
Averted: Bob dresses about the way you would expect a Prince to look.
Enforced: It's a stage or dance production where Requisite Royal Regalia is too expensive or cumbersome for the character -- they dress Prince Bob plainly and use minimal costuming and dialogue cues to show who is the ruler.
Lampshaded: "I'm surprised anyone takes Bob seriously as a ruler, given the gym shorts and baseball cap he's always wearing."
Invoked: Bob dresses in simple clothing to show that he is a selfless leader who won't spend extravagant sums on himself.
Defied: "By my crown, I will not be mistaken for some lowborn peasant!!"
Discussed: "That's the Prince? I thought he was the gardener!"
Conversed: "So, which one is the King again?"

Back to Modest Royalty, your Highness, but please...do something about that...tee shirt, was it? What would your mother, the Queen, bless her soul, think!?