Noises Off, Old Vic, LondonPippin, Menier Chocolate Factory, LondonFog, Finborough, London

Michael Frayn's play-within-a-play is as funny as ever in this slick production, while, across town, gritty new writers make their mark

All's quiet at the start of Michael Frayn's classic farce Noises Off.

The setting is a twee cottage presumed empty because it's up for rent. Inevitably, though, it'll soon be a riot of slamming doors and dropped trousers in the Old Vic's strongly cast revival – with Celia Imrie and Janie Dee on top form – directed by Lindsay Posner.

The lettings agent (Jamie Glover) has snuck in, off duty, with his bit of – well, the skirt doesn't stay on for long. What he hasn't allowed for is the pottering cleaning lady (Imrie), or the owners (Dee and Jonathan Coy) nipping in for a canoodle too, or the burglar, or the plates of sardines that materialise on every surface – multiplying slippery customers.

Frayn's clever twist is that this is a farce-within-a-farce. What we're watching in Act One is, in fact, a rehearsal for a farce (entitled "Nothing On"): a shambolic tech run which adds an extra layer of slapstick with jamming doors, props in all the wrong places, and the womanising director (Robert Glenister's Lloyd) being driven up the wall.

Most brilliantly, the set then spins 180 degrees for Act Two, and we watch "Nothing On" being performed again, but now on tour and seen from backstage as the company ethos goes from bad to worse. With amorous flings turning sour and much glugging of whisky, Lloyd's actors dash about behind the scenes sabotaging each others' entrances and exits.

It's uproarious, and the paradoxical delight lies in Posner's ensemble so deftly faking chaos, with split-second precision. That said, Frayn's first and third acts aren't so hilarious. To my mind there's something a wee bit dull in farce's regimented structures, emotional limitations and relentless pressing of the laughter button. Paul Ready stands out, making Lloyd's stage manager, Tim, touching as well as funny – on his last legs yet still trying to save the day.

Pippin, I fear, is beyond help. After a string of hit musical revivals, the Menier seems to have lost its touch with this cod-medieval saga, complete with 1970s pop score by Stephen Schwartz. Charlemagne's son, Prince Pippin, sets out to seize the day and excel in life, but is disappointed by all that he encounters: war, free love, politics, art ....

He's not the only one. Feeble-witted, cheesy and rambling, Pippin's escapades have been updated by director Mitch Sebastian to resemble a computer game. Harry Hepple's geeky Pippin is surrounded by snazzy graphics (designed by Timothy Bird), but also by risibly fey cyberspace-cum-Carolingian warriors. Think Ziggy Stardust clones auditioning for Ironclad, but prone to fits of Bob Fosse. Matt Rawle does his darnedest as the slinky, malign MC, eyeing Pippin and the audience with a wolfish grin. Frankly, though, seize the day and see something else.

Written by Toby Wharton and Tash Fairbanks, Fog is a gripping new chamber play. Set in a tower block, it's a disturbing portrait of a feckless white youth. Nicknamed Fog, he is played by Wharton with hunched shoulders and a mohawk haircut, emotionally vulnerable but potentially psychotic.

Trying to make amends for the past, his ex-army dad (Victor Gardener) rescues him from a care hostel only to turn rolling stone again. Fog joins a drug-dealing gang and – as his black childhood friend, Michael (Benjamin Cawley, surely a rising star), pulls away and starts applying to university – Fog's killing-spree fantasies intensify. The script specifies the characters' colour, though emergent racism hangs in the air only as a menacing possibility.

Fog might sound stereotyped, but the storyline's fragmented glimpses are intriguing, combined with an ear for Grime-influenced slang. Ché Walker's production – with a lone sofa in a raw concrete cell – is intimate, tender, terrifying, and occasionally funny, albeit that the comedy involves a slightly jolting gearshift.

While most folks are still recovering from hangovers, the Finborough has been the first theatre in the country to get rolling with a premiere. Artistic director Neil McPherson has, since 1999, worked tirelessly to make this tiny fringe venue in Earl's Court a trove of high-calibre new plays as well as rediscovered gems. Note for 2013: McPherson really should be on the list for a New Year's honour.

'Noises Off' (0844 871 7628) to 25 Feb; 'Pippin' (020-7378 1713) to 25 Feb; 'Fog' (0844 847 1652) to 28 Jan

Next Week:

Kate Bassett sees Frantic Assembly's Lovesong

Theatre Choice

Last chance to catch Arthur Ransome's Swallows and Amazons, staged with delightful imaginative bounce by Tom Morris (of War Horse) at London's Vaudeville (to Sat). And if you missed the illuminating and gripping docudrama The Riots at the Tricycle, catch it now at the Bernie Grant Arts Centre, Town Hall, Tottenham (also to Sat). It's also now or never for Mark Rylance's tour de force as the maverick gypsy in Jerusalem at the Apollo, Shaftesbury Avenue. Queue for returns until Saturday.