Comedy clubs are like people. They all have their own distinct personalities. Some – though not many – are quiet, polite and wouldn't hurt a fly. Others – most of them – are noisy and in your face. The country’s most famous club, The Comedy Store, clearly falls into the latter camp.

I don't go to the Comedy Store, currently in Oxendon Street, off Piccadilly Circus, as often as I used to, because there are so many other shows around town these days. But I'll make a special effort for Maxwell's Full Mooners, which has been running after the normal show on Thursday nights on and off during 2006.

This is one of those fantastically unpredictable one-nighters. It doesn't even kick off until midnight which immediately gives it an illicit thrill. The timing, combined with the witchy name, means that it attracts a lot of retro-goths, but then nothing is perfect and the compere, cape-wearing Irishman Andrew Maxwell, is so good I can forgive even being stuck behind a biochemistry student sporting more make-up than my mum and blocking my view with their back-combed barnet.

Previous shows have boasted guest appearances from Simon Pegg, who hadn't done stand-up for seven years, Paul Merton and Russell Brand warming up for his Edinburgh shows. I once spent an evening waiting for Michael Barrymore to turn up to do a rumoured comeback gig there, but, hey, you can't have a scoop every night.

Last Thursday, however, was a definite scoop. Blistering Bristolian Russell Howard opened and was truly on fire, dispensing killer gags despite some brutal heckles from a neanderthal contingent in the audience. After Howard came the real surprise. Direct from the Carling Apollo Matt Lucas appeared in the guise of Fat Fighter Marjorie Dawes, dispensing outrageous diet advice to all and sundry, which mostly consisted of advising slimmers to eat dust and bellowing "You is Fat. FAT!!!"

This is the sort of crowd-pleasing star turn that brings a gig to life. And more importantly, it shows that comedians aren't just in it for the cash. I'm sure that Matt Lucas is delighted that he is accruing plenty of dosh from Little Britain's record-breaking residency in Hammersmith but to me this impromptu cameo had greater significance.

When I recently interviewed Little Britain Lucas said that he would still be doing comedy whether he had made it big or not. I thought to myself that if that was true I'd eat my hat. But the fact that he is prepared to turn up for an extra show in the middle of a gruelling tour rather than go straight to bed and roll around in fifty pound notes makes me realise that he was being totally honest. I don't actually wear any headgear, but if I did I'd have had it grilled with a side order of chips by now.

Maxwell's Full Mooners, Thursdays, www.thecomedystore.co.uk