Thor and Loki always were up to something, because they were kids of course and didn't have anything else better to do and most of the ideas were Loki's.

One day, the day that both brothers get their helmets, Thor and Loki stole them early and were now giggling behind Odin's throne with the helmets on.

"This is heavy." Loki complained softly as the horns on his helmet caused it to fall forward. "That's what you get." Thor teased.