1.) Bug him about Mikeal.
2.) Call him, Nikki-poo, Nikki, or anything like that.
3.) (before he finds out why he can't make hybrids) pester him on why he can't make hybrids.
4.) make a bet with him that he can't drink as much blood as you can.
5.) Write a love note and say it's from Stefan.
6.) Tell him he needs to go into an insane asylum because he killed all of his family and brings their dead bodies with him.