1. Before he heads out to the training grounds, tell him his armour looks kind of big.

2. Then mention how it looks quite dull.

3. Ask him if he's made his daily quota for yelling at people yet.

4. After number 3, tell Arthur that he count Du in his daily quota.

5. Ask him to pout for you.

6. Go up to Morgana when Arthur's within earshot and say, "Doesn't Lancelot have nice hair? He's so much cuter than Arthur!"

7. For added effect on number 6, add "Lancelot isn't a prat, either!"

8. And if Du want to be REALLY mean, add "No wonder Merlin likes Lancelot better!"

9. During a conversation with...