Personally, I don't see Cullen as being "naughty" per say... I just see him finally being comfortable with the Quizzy enough that he loses the shyness & let's down his guard to actually say and act how he feels without the threat of ridicule or rejection. He's now confident in knowing she'll enjoy or like what she hears because she's totally into him. I think a lot of people are like that.
Being an introvert myself, that's exactly how I feel.
This is why I sympathize so much with the Commander. It's like staring into a mirror, acknowledging all the faults.
I'm unable to act naturally and show my true feelings for someone until I become used to them.
Spontaneity only surfaces after trust's been established.
Most people just lose their patience, though, and think I'm cold, insensitive, snobbish or arrogant.
And then, I torture myself, trying to find a way to show them how I truly feel.
But it's difficult. The natural reaction of an introvert is: Think first, act later.
People think introverts do this on purpose, but it's out of their hands.
No wonder Cullen is always apologising for his stuck-in-the-mud, shy behaviour. He's aware of this peculiarity in himself, but can't change who he is.