Sadie: lol, Hi!
Well, hm…since I just got the sexual anon, I’m going to take ‘naughty’ to mean in an adult context. Everyone can have their own take on how the characters would react, but if you’re asking me what I personally think?
Sherlock gets very wide-eyed and coy. John’s biggest clue that he’s feeling that way is that all the babbling and baby talk stops completely, and the word ‘Daddy’ takes on a specific enunciation.
When it’s Jawn, he gets very, very mischievous and bratty, in a “What’cha gonna do about it, Daddy?” >:)-sort of way.