This bloke's in bed with his missus when there's a rat-a-tat-tat on the front door. He rolls over to look at his alarm clock, and it's half three in the morning. "Sod that for a game of soldiers", he thinks, and rolls over. But, a louder knock follows.

"Aren't you going to answer that?" asks his wife, so he drags himself out of bed, and answers the door.

"Eh mate" says the stranger, "can you give us a push??"
"No, piss off, it's half three. I was in bed" says the man and he shuts the door.

Back in the bedroom he tells his wife what happened but she says "Dave, you're a right git. Remember that night we broke down in the pouring rain on the way to pick the kids up from the babysitter and you had to knock on that man's house to get us started again? What would have happened if he'd told us to piss off??"

So he gets out of bed again, gets dressed, and goes downstairs. He opens the door, and not being able to see the stranger anywhere he shouts: "Eh mate, do you still want a push??" He hears a distant voice cry out "Yeah, please mate." So, still being unable to see the stranger he shouts "Where are you?"  The reply comes back - "I'm over here on the swings."