Disclaimer: I do not, nor will I ever or have ever owned Full Metal Alchemist
--- Quirks ---
She hates the way he always leaves the toilet seat up, he hates the way she always uses fruity body and hair soap. She hates the way he always tosses his dirty clothes on the floor and he hates the scent of the fabric softer she uses on the sheets and clothes. She hates his annoying obsession with candles, he hates her annoying obsession with guns. She hates junk food and he hates health food. She hates his hard rock music, he hates her soft classical music. She hates his parents, he hates her parents. I guess opposites do attract.
A/N - I looked up 'quirk' and saw 'characteristic' was a description of it and went along with that as a theme. It's the same thing, but more broader to work with.