Headcanons, and a question for writers

Does anyone else have really weird or unusual "headcanon"? (Note that when I say headcanon, I don't mean stuff I think should happen in the series. I mean stuff I think could plausibly be in the series and would be pretty funny. Also, the stuff in my writing is rarely my headcanon. Hell, I have two different origins of the Pony world stories in my head that completely contradict each other!) So far I haven't met anyone else with some of these headcanons. For example,

Rarity is secretly a huge football fan.

Reasoning? Her dad's cutie mark is three footballs. He might be a football coach, and Rarity and her family go out and support the team passionately. Mostly though, I just find the mental image of Rarity being one of those ultra-mega fans who paint themselves with the team colors and scream themselves hoarse to be intensely funny.

Also, Rarity is secretly a comic book nerd.

Reasoning? She designed the Mare-Do-Well costume. She might have gotten inspiration from an old favorite hero. But mostly, I mostly find the idea of her secretly liking something so "boyish" to be really charming.

And another thing. I don't know if this one is unusual or not, but Rarity's a bit young to need reading glasses. Far-sighted maybe?

Applejack lived in Manehatten for quite some time. This is actually something I will(and have) write about, because I think it has potential for a lot of comedic moments and character development for AJ, who lately has been something of a muse to me for some reason. But anyways, I have two reasons for thinking this; one is that AJ states she was younger than the Cutie Mark Crusaders when she moved to Manehatten, but was the last kid in her class to get a cutie mark. This suggests to me that some time passed between the two events. Two is that Applejack is able to speak with barely a trace of her accent, and speaking as an Arkansan, the "hokiest, barefootedest, most ho-down state this side of the Mississippi" that is incredibly hard to do, especially for a kid. Your accent is a stamp, a tell-tale sign of your upbringing, and to make a conscious effort to conceal it is very difficult, unless you're a highly skilled actor. There are classes adults take to learn to conceal your accent, in order to make a better first impression or be more understandable. Somehow I find AJ learning to do that in a few days really hard to swallow.

Another random one; AJ has guilty love for musicals. Based somewhat on my Manehatten theory, the idea came about that AJ went to see a lot of musical theater while there, and nowadays its a guilty, nostalgic pleasure.

And that's some of mine. What's some of yours?

Also I have a question for some of you writers. What do you do when you become far more interested in another story rather than the one you're working on?