The Wonder of Sex, RNT Lyttelton, London;<br></br> Aladdin, Theatre Royal, Stratford East, London;<br></br> Time and the Conways, Royal Exchange, Manchester

Time for a post-coital nap...

Maybe there is a profound connection between carnal pleasures and laughing. Sigmund Freud noted there was much punning in symbolically erotic dreams as well as in his favourite jokes, and The Wonder of Sex, performed by the zany National Theatre of Brent, certainly had some spectators in hysterical giggles last week. This is alternative entertainment for the silly season and, be warned, there's some audience participation. But the NTOB – aka pompous Desmond Olivier Dingle and his assistant Raymond Box – principally arouse laughter by failing in their attempts to re-enact legendary moments from the coital history of humankind.

Our comic duo hype the show as a groundbreaking hi-tech affair. However, Dingle (played by Patrick Barlow) clearly isn't master of his remote control, for the theatre's velvet curtains cascade downwards, leaving only four waving legs visible. Elsewhere, sound cues and video snippets go awry as Dingle and Box wobble into view on motorised rostra, dressed as Oedipus, Rasputin or Lady Chatterley – usually with just another hat atop their trademark grey suits.

The absurdity is that our hosts are manifestly hopeless innocents in respect of both acting and seduction. Box (John Ramm) is like a mentally-challenged child, throwing strops or eagerly repeating lines he's mislearnt by rote. It is rather delightful watching a "sex show" that's more naïve than your infant school nativity play. Of course, Barlow and Ramm have been honing their faux-ineptitude for years. Their mix of grandiloquence and defective grammar is particularly inspired – as when Box's Salome clumps in, tosses seven hankies about and demands, "What might you give unto her if she done the dancin'?". That said, while the gent in front of me was wheezing with amusement, an adjacent punter was looking at his watch. Clearly the NTOB can't tickle all of the people pink all of the time, and two or three sketches dragged for me. Moreover, I caught this company's Nottingham Playhouse show, The Mysteries of Sex, four years ago. That's referred to in the RNT programme as the second of the company's Sex Trilogy (after 1984's The Complete Guide to Sex), but much of the 1997 material has just been reworked here. I felt cheated.

A more obvious romp for parents with kids in tow is Stratford East's Aladdin. Oh yes you can stage a genuinely charming panto, and this one is a notably ebullient occasion since the Theatre Royal has been dark for four years during refurbishment. Decent backstage facilities and two bars are now provided, while inside the cosy Victorian auditorium you find the cast's Oriental costumes glowing like jewels. Overall, Kerry Michael's production is a happy mix of ethnic influences and trad British ingredients (sweet-hurling, sing-alongs and so on).

David Cregan's book and lyrics aren't amazingly witty and there are too many musical numbers. Nonetheless, highlights include the final, life-enhancing jitterbug and chorus of "We Got Magic Too". Kat B's Aladdin is acrobatically bouncy and Sarah Rajeswaran, as his princess, is a sturdy innocent who shuns her relatives' uppity attitudes. Though I wasn't blown away by the genie (two waggling giant lips), Michael Bertenshaw is a droll, gruff dame without the usual camp Twanky clutter. Actor-composer Brian Protheroe is a laughably villainous Abenazar and the audience rapport is as lively as ever. A hearty welcome back.

Manchester Royal Exchange, meanwhile, offers a would-be quality period drama. Unfortunately, JB Priestley's Time And The Conways, rather than feeling like mature fare, comes across as creaky and unsophisticated. Initially, we see well-to-do Mrs Conway celebrating one daughter's coming of age and her favourite son's return from the Great War. But cutting to the eve of the Second World War, we find sour domestic quarrels.

Allegorically, this reflects international relations. In Braham Murray's production, a moustachioed Ian Pepperell resembles Hitler as he plays the snubbed "little man", Ernest Beevers, who threatens the Conways' cosy world. The sniping can be entertaining and Priestley, typically, exposes snobbishness. Nevertheless, this piece largely comes across as sub-Chekhovian, especially since Murray encourages caricatured acting.

Portraying Mrs Conway, Gabrielle Drake ages so hammily that my toes curled in response. And Priestley laboriously spells out his thematic interest in life's medley of joy and woe, starting with the youngest Conway's cry: "Just when everything's very jolly and exciting, I often think of something awfully serious." Ironically, the Conways' deadly, passé style of talk runs against the play's central philosophical lecture about time being one continuum instead of a series of decaying moments.

This year has seen several Priestley plays given high-profile revivals, including the modern-dress Dangerous Corner in the West End. Still, I remain far from persuaded that his oeuvre is evergreen.

k.bassett@independent.co.uk

'The Wonder of Sex': Lyttelton, RNT, London SE1 (020 7452 3000), to 16 February; 'Aladdin': Theatre Royal Stratford East, London E15 (020 8534 0310), to 26 January; 'Time And The Conways': Royal Exchange, Manchester (0161 833 9833), to 19 January