minor headcanon

• His shortness is partly (but not entirely!) his automail's fault for being so heavy. At the point he's taken from canon he still has some growing to do, but will cap out at the lowest end of average in two or three years' time if he doesn't either switch to lighter prosthetics (as he later had to in Germany) or get his original limbs back again.
• Often transmutes his own clothes, and keeps spare fabric around for them if possible. If he's been in a lot of fights lately, it's probably faster than buying them.
• He went to school right up until Izumi took him and Al on as apprentices, but didn't like it and often stayed home to read books. He hasn't had any formal education since.
• Learned how to use chopsticks from Izumi.
• Likes cats, though he's a little reluctant to admit it. They're his favourite animals, actually.
• He knows nothing about music beyond stuff like acoustics, but he'd have a decent singing voice if he ever tried... which is unlikely.
• His mother was the only person who's ever called him tall.
• Although he knows the energy for alchemical reactions doesn't come from plate tectonics, that's still the explanation offered in all of the textbooks, so it's the answer he'll offer first if pressed on the subject.
• When he temporarily regained his limbs, they displaced his automail but not the sockets it plugged into. This would have been painful and probably would have required surgery sooner or later, but happily(?) that was moot; it did mean he wasn't bleeding out the moment he arrived in Germany on Hohenheim's doorstep, although his clothes were badly torn up from the trip.
• Generally finds fiction reading dull, but will pick up comic books if really bored (and if nobody else is watching too closely). The cheesier, the better.
• Amestrian physics and to a lesser extent maths lags somewhat behind Earth's compared to its chemistry, biology and geology. In particular, nobody has seriously entertained the idea of relativity, and the equivalents of Newtonian ideas hold a lot more clout - so light is usually described in terms of corpuscles instead of waves, and mathematical problems will have infinitesimals all over the damn place.
• Except where explicitly seen to be different, which IIRC applies pretty much just to Liore, the geography of this continuity's world is the same as in the manga continuity, names and all.
• The same obviously isn't true of history, but a lot of notable events are similar as far as metaphysics allows, although their exact dates may be seemingly arbitrarily shuffled around to greater or lesser extents... a bit like the actual adapted events and conversations in the series.
• In particular, Xerxes existed and there's still a legend about it being wiped out in a single night by the Philosopher's Stone - said legend is mentioned in the anime, but not the name - but the story was exaggerated by Dante (whether or not she was actually responsible) and, like with Liore in the series, some people did get away.
• As such (or maybe not), gold is just a weird eye colour. It's uncommon, probably recessive, and striking enough to be a useful physical descriptor, but doesn't signify anything.