"A Bigfoot."
He saw his feet were getting bigger and bigger and bigger and bigger and bigger and bigger and bigger and bigger and bigger!
Then, suddenly, his body increased in size, splitting the clothing apart. Also, thick brown fur grew on his body, changing the coloured his hair from grey to brown, and on the tops of the enlarged feet.
He was now bigger and taller, and his coat and shirt were now reduced to that of a waistcoat, and his pants were reduced to shorts.
Arlo should have been devastated by what he'd become, but he liked it.
"Who cares about being a human anyway!!!" He yelled, and raced out into the forest, cheering and whooping.