1. Sherlock doesn't like the colour orange. He doesn't like most colours, but orange is his absolute least favourite. It's why he loathes the shock blankets so.
2. John manages to kill every plant he's ever owned, even that cactus that Harry got him. (She thought it was hilarious that the doctor couldn't keep a simple plant alive.) Living with Sherlock, it's probably for the best, because otherwise they'd end up as experiments.
3. Sherlock loves cats, but is allergic to them. John thought about getting him one of those hairless ones after the case where the hairless cat kept sitting on him, but finally decided it was too ugly.
4. Mrs Hudson made that Christmas sweater for John as a joke. John didn't realize that, and pretended to like it. Mrs Hudson thinks that he actually likes it. They both feel bad.
5. Sherlock never liked dogs, and the case with the hound really made him not like dogs.
6. Those crisps that Sherlock brought for Molly instead of letting her go out for lunch? They're her favourite. Sherlock made sure to get that kind.
7. Mrs Hudson didn't really need Sherlock to get a flatmate to share the rent with, she just didn't think it would be good for him to live alone. So part of the deal was Sherlock had to get a flatmate. (She's quite pleased with herself for that.)
8. Moriarty wasn't 'playing gay', he was just... playing it up a bit. He told Sherlock it wasn't true because he didn't want to be judged.
9. John did get a Christmas tree that year they were doing the case with Irene, but Sherlock managed to 'accidentally' light it on fire before the party.
10. Sherlock loathes alcohol. He doesn't like drinking it, he doesn't like smelling it, he doesn't like when John drinks it, and he doesn't like having any in the flat.