My son, Julio, was telling me he was nervous. "It feels like a helicopter in my tummy."
I told him that most people describe it as butterflies. Then I explained that the tingly feeling was caused by your body sending the blood away from digestion and towards to the big muscles, making you strong for an emergency. "So the heli in your belly gives you more welly."
When you're nine years old, that sort of thing is hilarious.