Care Package

Billy hadn't done this before, and Uncle Graham had left no instructions - but the place seemed nice. He napped until footsteps woke him, then he roared.
"Who's that trip-trapping over my bridge?"
The girl teenager didn't break step.
He'd been hoping for a goat, anyway.
Billy roared at another teenager, but they just mumbled "cool costume, bro" before hurrying on.
It grew dark. Billy was very hungry, but when he heard more human footsteps he roared only half-heartedly.
The old lady smiled.
"'Trip-trapping?' I've not heard that in decades. I know Graham's away. I've brought you a roast beef sandwich."