Embarrassed
Loki could feel his cheeks burning, he could only imagine what he looked like.
"Loki!" Thor called out, "Are you playing 'barnyard animals' with the little children? Why do you have horns on your head?"
"Shut up, Thor," he hissed through his teeth.
"Are you a cow?"
"SHUTUPTHOR."
"You make a rather fetching cow, brother!"
Loki's face grew redder. He turned to his mother.
"Are the golden horns really necessary?"
"Oh hush Loki, you look very handsome, ignore him."
"But mother," he complained, "I mean, did the helmet need to have horns?"
"Loki they look fine, you look fine, just cease your childish whining!"
Thor re-appeared, sporting his new helmet. Loki took one look at him and his flushing face, and began laughing uncontrollably.
"Nice feathers, Thor!"