Nickname for baby

Ca
My dad started calling my baby-to-be "brat" (he used to call me that) and I really don't like it. He says is open to suggestions of alternatives and suggests "sprog" or "carrot" (my baby's real name will be Jasper)
I really don't like these much either but can anyone suggest something short but that he might go for. I wish he could just use his name, but this is my one opportunity to start something better. He calls their cat Molly "fat cat" so I want to get in quick with something that my child is less likely to resent in the future.