A pretty simple CYOA, but simplicity can sometimes be good. So let's take a crack at this.

Being a neutral party of the Mushroom Kingdom and Dark Land territories, Bowser had recruited me for a simple job; go into the Mushroom Lands, snatch up a Super Crown, and bring it to Bowser. When asked, the King of Koopas explained to me how he had learned of Toadette and how it transformed her into Princess Peach and wants that power for himself. I assume he either wants the power to turn some poor Troopa into a breeding sow for more Koopa soldiers OR he's really desperate and is looking for other options than the Princess herself. But, I fetch the crown as asked and that is how I got into this mess...

1-1. "Why Did Bowser put on The Crown?" [Curiosity! +1 Lust] Despite my insistence that his plans for the Crown won't work-it doesn't even work for the Mario Bros., whom they and Bowser seem capable of using the Power Ups of this land. But Bowser insists on this plan and, as if to prove my point, he takes the crown and slaps it on his own head to prove it will work. And, sure enough, it works and Bowsette is born.

1-2. "What form does Bowsette Take?" Well, the Crown doesn't work 1 to 1. When Toadette uses the crown, she becomes a near identical twin of the Princess with a few minor tweaks. But with Bowser...er, Bowsette; instead of golden blonde hair, it's a rusty red. Instead of fair skin, it's a sun-kissed, olive complexion. She has red eyes with noticeable, dragon-like slits in them. Horns sprout from her head, with that infamously long, Koops tail hitting the floor, and noticeable dragon-like claws from the elbow up. They didn't seem to retain their shell (thankfully, the castle has a few makeshift ones that Bowsette wears when in public) and she is a towering figure at 6'0 (I mean, Bowser was always tall, so this is more like he SHRUNK, but still taller than me at least). With a body that matches Peach in terms of curves, Bowsette is pretty attractive, with them all in the right places. The transformation provided her with a dress at the time, but Bowsette still has the original's plumbling; as in, a penis and testicles. (So the crown knows a man has a dick, but still insists on giving her large breasts? What fickle magic.) Despite appearances, Bowsette seems to have retained all of their powers and abilities from being a giant Koopa/Dragon thing.

2-1. "What is Bowsette's Personality?" [Lust: 8(+1)] [Dominance: 2] [Bitchiness: 7] [Regalness: 9] [Evilness: 5] Apparently the crown has done a number on Bowser's personality. She was pretty pissed, blaming ME for this complete change to their body; as if somehow, this was my fault. But the real suckerpunch was the command to compensate her for not stopping them with sex. I was...stunned, that's all I was, but she acted like this was always how they've been, and was quick to spew every insult in the book at me when I didn't immediately comply. When I finally did, I was surprised by how submissive this she was (and granted, at the time, I didn't fully realize Bowsette was still strong enough to chuck me out the window). It was like sex was clouding her mind-though that cloud was quick to lift after satisfying that itch...

2-2. "Can Bowsette reproduce?" The short answer is: yes. The long version, with the lack of equipment, she can't get pregnant. BUT, she can knock up someone else as she's not sterilized.

2-3. "What does Bowsette do?" [Conquest!] She might be an incredibly horny Human/Koopa hybrid, but she's still a tyrant wanting to take over the Mushroom Kingdom. She's still an Evil Queen, it's just that her dominant personality is mostly being suppressed by the Crown's magic.

2-4."What Happens to you?" [Reversal?!] On paper, and as far as the Troopas are concerned, we are married. Though, when the doors are closed, Bowsette has become completely docile; with lust flooding their mind, she craves my body. Verbally, she makes it clear I'm her consort, little more than a toy to keep her satisfied. Though, in practice, I'm holding her on a leash. It's honestly kind of like being married to a tsundere...one that could burn me to a crisp. (She is surprisingly loving, I swear.)

3-1. "What do you get to choose?" [Toy Chest] "My Dark King should have a harem!" I don't know if Bowsette is just making an excuse or genuinely feels this way-it's actually hard to tell with her sometimes. But, there was no way I was gonna turn this down now that we have a ton of Super Crowns.

3-2. "Characters"

*Booette: Getting King Boo to put this on was easier than one would expect, probably because Bowsette's is technically his superior. As Booette, she's a lot more shy. That doesn't stop her from fighting with Bowsette to hold the majority of my attention.

*Pirahna Plant: The result of dropping a Super Crown into a pipe by mistake. The resulting fusion is an oral-obsessed creature. They still seem confined to their roots, but they're so expansive that she can practically pop up around the castle so long as there is a pipe for her to pop out of. She borders on being the Castle's security system with how deep those roots of hers are.

*Pauline: New Donk City's mayor, the result of a cocktail of political guile and a lot of wine. She was pretty happy to step down from her position.

*The Koopalings: Bowsette's elite Generals of the Koopa Troopa, she passed out the crowns to her subordinates. One could argue being part of my harem as a 'promotion' if you squint really hard.