I have a few, actually! I'll just name three for each character to keep it short.
Sherlock: His favorite instrument is the piano, despite the fact that he plays the violin. He detests grocery shopping, and will try and just get food from corner stores and street markets as opposed to larger stores to avoid the noise, the lines, and general aggravation of the experience. Despite being an intelligent boy, Sherlock used to get kicked out of his classrooms for correcting his tutors and disrupting the lessons with "inappropriate questions."
Steve: His favorite meal of the day is breakfast, but he kind of sucks at cooking so he sticks to very simple meals. His favorite colors are blue and white, and his least favorite is red (funny considering the whole Captain American thing). At least one person on his mother's side has had an "S" name so far back as they can trace; his name is Steve, his mother's name was Sarah, his maternal grandmother's name was Sinead, his great grandfather was called Sean, and so on.
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What has been the hardest part about pretending to be human for Sebastian?