The thing that most american sherlockians don't realize is, in England "trousers" are "pants", and "pants" are "underwear". John isn't talking about Sherlock's pants he's talking about his underwear. One of my favorite scenes.
"This scene breaks my heart cause Sherlock thinks its the last time he is going to see John and he wants to say so much but what he wants more than anything is to see John laugh! He is MEMORIZING John’s laughter!<----i cant