Fire Retard
"Hey Katara, this dress has a warning label."
"Let me see?"
Katara pushed aside her brother and grabbed at the dress in question, a grubby brown dress in a large street-stall. Sure enough, there was a small hand-sewn label with a very stern warning that the "garment is not flame retardant" on the front.
Sokka let out a loud laugh. "What the hell is a flame retard?" he asked loudly, while Katara elbowed him and hissed "retardant, stupid" at him.
"Retardant, retard, same thing. Still, do you think there is a flame retard? What if it's Zuko? Or a retard on fire?"
Katara stomped on her brother's foot, her cheeks coloring at her brother's thick-headedness.
"You insensitive imbecile, shut up!"
Sokka gazed at her queerly.
"Why'd you—ow! But Katara, why's it bad that Zuko is a flaming retard?"
A nearby Fire Nation soldier nearly dropped his groceries.
"I never knew Prince Zuko was gay or retarded!" he whispered to himself.
The market soon accustomed to the cries of "—ow! Katara, I'm sorry! Stop, please!" as she mercilessly "educated" her brother on how to be polite in public.
From the author:
I can see people getting offended at this, so I'll clarify where this came from. A friend of mine has a brother who is in the second grade, and we happened to see this particular warning label on a blanket while were at Costco. He of course immediately piped up in the loudest voice possible, making more than a small scene and likely offending everyone within a hundred yard radius. Thus, inspiration, as Sokka occasionally has the mentality of a 6 year old boy.