"Need a Push" joke

A man and his wife are awoken at 3 o'clock in the morning by a knock on the door. The man gets up and goes to the door where a stranger is asking for a push.
"Not a chance" says the husband -- "It's three o'clock in the morning!" He closes the door and returns to bed.
"Who was it?" asks his wife.
"Just a stranger asking for a push" he answers.
"Did you help him? she asks.
"No I didn't -- it's three in the morning"
"Well you've got a short memory" says his wife, "Can't you remember about three months ago when we broke down on holiday and those two guys helped us?. I think you should help him."
The man does as he is told and returns to the front door and calls out into the dark "Hello -- are you still there?"
"Yes", comes the answer.
"Do you still want a push?" calls out the husband.
"Yes please!" comes the reply from the dark.
"Where are you?" asks the husband
"Over here on the swing" the man replies.