FILM / 10 Twin Facts: Hollywood has a quiet obsession with twins. John Lyttle considers the similarities

1) One twin is Good. The other is Bad. Or Weak / Strong. Rich / Poor.

2) Twins are often Separated At Birth.

3) Twins are often telepathic.

4) Twins often take each other's place. The dog always knows when his master / mistress is being impersonated. He growls, while another character says: 'I don't know what's got into old Rex.'

4) Girl twins invariably fall for the same man. Dumber than the average dog, the husband / boyfriend only suspects there's a substitute on the field when the stand-in refuses to have sex. Also, her kiss is somehow, well, different.

5) Visual cliche: the over-the-shoulder shot with the stand-in's back to the camera. We see the star emote to the 'twin'. Reverse shot. Star now takes stand-in's place. Emotes again. We are poleaxed by such versatility.

6) Visual cliche: twin passes object - cigarette, comb, pen, etc - to other twin in the same shot.

7) Visual cliche: twins fight. Much rapid cutting and discreet face hiding by the stunt team ensues, all to ensure the illusion that a titanic clash between two identical people is occurring.

8) Speaking of which, there's usually a scene with the twins preening in the mirror: four for the price of two.

9) Movie twins have similar tastes in costume designers and make-up men.

10) An offending object - the other twin's cigarette, comb, pen, etc - or uncharacteristic behaviour exposes the impostor in time for the final credits.