'You can't come in just your pants,' I said, as I hurried to make my escape.
So he went and got ready.
He put on his shoes and his sunglasses.
One day I'll call his bluff and take him in the car with me. But knowing GrandSon2 he'd be perfectly happy and we'd end up with GrandSon2 having an unplanned sleepover. (Thus making GrandDaughter1 cross and leading to us then having her to stay and so on ...)