This is going to be a little complicated, because my daughter "Jenny's" name is not really Jenny. So trust me when I said that I like to call her, "Jenny-hopper," it makes a lot more sense (sound-wise) with the diminutive of her actual name. So, for some reason, when Jenny was a baby, I started calling her "Jenny-hopper." This led to "Jenny-hoppy" and sometimes "Hopper" or "Hoppy." So she seriously goes by "Hopper" or "Hoppy" half the time, and it's really cute.
The other day, we were driving back home from somewhere, and she started talking in a serious tone. "Mommy, now that I am 4, I think I don't want to be Hoppy anymore."
Me: "Oh, yeah? So you want us to call you Jenny from now on?"
<thoughtful silence> "No. I want you to call me "Hop.""
Ah, those little Hoppies. They grow up so fast.