A visitor from another world – or just a dirty old man with a ladder?

If, this time next week, we are all under the control of superior beings from the Planet Tharg, remember you read it here first.

Grainy footage of what a film-maker claims is a gentle-looking, youthful alien was unveiled to the media of an extraterrestrial-obsessed United States in Denver on Friday.

It shows a white, balloon-shaped head, not unlike the face in Edvard Munch's The Scream, bobbing up and down and blinking outside a windowsill in Nebraska.

In contrast to the famous features of the fictional ET, the skin of the creature appears unwrinkled, rather similar to, for instance, that of a widely available Halloween mask. But if the image is of an alien, they may not be quite as benevolent as they appear.

The film was shot by a Mr Stan Romanek after he became concerned that someone – or something – was peering in at the window of his teenage daughters' bedroom. So he set up a camera, with the result you see below. Thus, the creature that journeyed at the speed of light through interminable galaxies to a Nebraska suburb may, in fact, be the advance guard of a race of super-intelligent peeping Toms. And, since the windowsill is 7ft above ground, our visitors are not so much little green men as rather tall dirty old men. Either that, or the alien took the trouble to bring his own ladder.

The film, to be included in a forthcoming documentary, was presented to a surprisingly under-whelmed gathering by Jeff Peckman. He believes it is "irrefutable evidence" of a visit from another world, which makes it a very timely, since Mr Peckman is trying to get his city of Denver to create a task force to deal with space aliens.

He is sure they have been to Earth in what many of us would regard as surprising numbers – perhaps as many as 57 different varieties, he said with a straight face.

Mr Romanek's video is around three minutes long, in black and white, and was taken at night. The otherworldly face – or head on a stick, depending on your point of view – popped up to stare in at the window four times. It was made on 17 July 2003, and Jerry Hufmann, of Colorado Film School, said he believed that it had not been doctored in any way.

Media were barred from recording the moving images at Friday's press conference, but a still was made available. Already, spoofs of it abound on the net. And, who knows, somewhere up there, amid a million stars, a group of intergalactic perverts may be planning their next visit to peer in at an Earthling's bedroom. It could be you.