A Martian Comes to Stay — Penelope Lively

The Martian's spaceship needs repairs, but when he returns with the spanner he's borrowed from Peter and his gran, he finds he's been abandoned! Luckily, Gran and Peter take him in, and introduce him to life in the country. It's all going well until they take him to the village fete. Will the local villages see through the Martian's cunning disguise -- and what will happen if they do?