"Hit your head against that rock."
"Why?"
Stoic stared in disbelief at his son, "What?"
"Why should I hit my head against a rock?" Hiccup was only four, but he already seemed so much like his mother, who happened to be watching the scene with amusement from their house, "It doesn't make any sense."
"How could it not make sense?"
"Well," the boy started, "I get enough headaches when Snotlout and Tuffnut throw stuff at my head. If I hit the rock with my head, I'll just get ANOTHER headache."
Back in the house, his mother was cracking up laughing at the look on her husband's face. It wasn't often Hiccup talked back to Stoic, but he made a good point whenever he did.
"And," Hiccup continued, "If you haven't noticed, I'm the human equivalent of a stick. I can't even lift the rock."
As if to check his son's theory, Stoic picked up the reasonably sized rock single-handedly and put it in Hiccup's arms. It immediately fell although the boy tried to catch it.
"See?"
"But you don't need to lift it to hit your head against it."
"But you still haven't explained why I need to hit my head against the rock."
"I don't need to explain; that's the point!"
"What point?"
"Will you quit stalling!"
"But it's pretty much the only thing I'm good at!"