Zuko and Katara aren’t all that fond of pet names for each other, but for their kids? That’s an entirely different story. And those terms of endearment tend to reflect their partner’s nation of origin rather than their own.
Zuko: “How was your bending lesson today, snowflake?”
Katara: “Come here, firefly, let mommy take a look at that scrape.”
Zuko: “Okay, little moonbeam, it’s time for bed.”
Katara: “”Eat your sea prunes, sunshine.”
The exception? They both use “turtleduck.”