What does Momoshiro call Ryuuzaki-sensei when he talks to her? When he talks about her?
What do you think Kaidoh would call Tomoka? Just Osakada? (Not pairing them up, at least not at the moment...) I don't always have a good sense of what he would call people, especially girls, since I don't think we ever see him talking to any.
I was very, very charmed by Toudou calling Hiromi "Oka-kun" in the Ace wo Nerae drama but don't quite dare to use that in tenipuri fic.