Is it a bird? Is it a plane...?

No. It's the Incredible Sulk.

This monster takes on many incarnations. You may have one lurking across the room on the other sofa at this very moment, sighing audibly whenever your laptop keys click slightly louder than a gnat's stiff knee joint. It has probably already cranked up the volume on the TV and muttered, "Is it too much to ask to be able to hear The News?" Whatever you do, do not look over at it - and control your sniggers.

Apprentice monsters adopt the posture of a ricket-afflicted Victorian clerk; hunched shoulders, a lowered gaze. They grow their hair over their faces and communicate only in a sullen mumble - like grumpy ventriloquists. Favourite expressions include It's SO unfair! But everyone else does! It's my room anyway! You just don't understand! And so on ... (Assume all pronouncements end with an exclamation mark).

Younger Incredible Sulks have yet to perfect the pervading, angst-inducing silence that indicates their displeasure, preferring to rely on a steady percussive beat of slammed doors, broken dishes, and Radio 1 turned to maximum volume.

Advanced Incredible Sulks work on the premise that silence throbs.

Perhaps Incredible Sulk rampages round your house when its team has lost to Manchester United? Does it lie moaning on the bed? A mantra that sounds something like "There is no way that was a penalty/foul/offside*." (*Delete as appropriate).

Maybe your Incredible Sulk emanates overtly hostile gamma rays? Perhaps it takes to its bed for whole weekends? The bedroom door firmly shut, the occasional - but very significant - heavy creak of floorboards and the flushing of a toilet the only physical manifestations of this malign presence.

Incredible Sulks are delighted when you get that job you wanted so badly or if you are excited about something. They are especially fond of birthdays, Mother's Day and Christmas. These important dates are marked in red on the calendar as superb sulking opportunities.

Take Incredible Sulks to the theatre, ballet and cinema. This is something they adore. An expensive restaurant will do just as well - though, if you wish your monster to display their full sulking capabilities, ensure that the waiters are attentive and the room candle-lit.

The Incredible Sulk will transform into a large lump of granite; glowering and darkest grey. Above its head hovers a radioactive cloud of extreme displeasure. There are speech bubbles, with dots to signify thoughts: I am not enjoying this, I don't want to be here, I especially don't want to be here with you.

Hold your breath and count to ten. This cloud is poisonous if inhaled.