Elling, Bush Theatre Rafta, Rafta, National Theatre, Lyttelton, London

For the first few minutes, I thought I was going to cringe through Elling, Simon Bent's stage adaptation of the cult Norwegian movie. It looked as if we were in for a Dumb and Dumber of the dysfunctional world - one of those shows that invite you alternately to laugh at the loonies and to feel good about yourself for patronising them with sugary sympathy. Gradually, however, the uncynical, positive spirit of Paul Miller's well-judged production and the winning depiction of the central relationship won me round.

A variant on the Odd Couple formula, the piece follows the fortunes of two middle-aged men after their discharge from a mental asylum where they were room-mates. Assigned a state-subsidised apartment in Oslo, they are offered the opportunity to prove that they can lead independent lives. Given the range of their compulsions and phobias, the chances of success initially look slim.

The title character is a buttoned-up fusspot who lived with his mother until her death, whereupon he became so insecure that he took to sleeping in the wardrobe. His mate Kjell is a sex-obsessed giant who, at 40, is still longing to lose his virginity - an ambition not likely to be furthered by the fact that he has no conversational skills and forgets to change his underpants for days on end.

The temptation to remain house-bound is strong, and when outside interest arrives, it creates tensions in their relationship. Kjell finds love with a pregnant neighbour, and Elling, who has come under the influence of an old poet, starts smuggling copies of his own verses into packets of sauerkraut in random supermarkets - a potty, secret agent-style method of disseminating his work that suits this self-important but inhibited man.

Yes, it's too neat and sanitised and the play seems to raise potential problems (the old poet's half-desire to exploit Elling; the dangers to the neighbour's late pregnancy of Kjell's inexpert ardour) only to flick them aside. But the leading actors succeed in making you care about these oddballs.

Adrian Bower brings out the gentle, protective soul of the lumbering sidekick, while the splendid John Simm captures the essence of Elling in a performance where the spasms of fastidious disdain, palpitations of anxiety and bouts of big-head bluff are registered with pin-point accuracy.

Have you heard the one about the young couple who get married, move in with the groom's family and then can't consummate the union because of the thin walls and an overbearing father who would put Casanova off his stride, let alone a nervous male virgin?

This was the plot of All in Good Time, Bill Naughton's 1963 Northern comedy and its cinematic spin-off The Family Way. Now, at the National Theatre, Ayub Khan-Din transposes the archetypal scenario from the white working classes of the Sixties to the Asian community in contemporary Bolton.

Naughton's good-hearted but interfering patriarch becomes a first generation Indian immigrant who is portrayed here in a gloriously funny performance by Harish Patel. A podgy, unstoppable extrovert, he's disappointed in his reserved, directionless older son Atul (Ronny Jhutti).

Khan-Din's script brings home the conflicting pressures on Atul, who is expected to integrate (but not to the extent of preferring Dvorak to bhangra) and to succeed (but not if this involves becoming arty). The Oedipal conflict is translated into lovely, broad farce, with Tim Hatley's design letting you see the inhibiting effect of the father's physical proximity in its four-room view of the crowded house.

Nicholas Hytner's production generates waves of good will in its warm-hearted, buoyant depiction of Indian domestic life and there's spot-on acting from a crack cast. Meera Syal brings just the right blend of stoicism and asperity to the role of the sorely tried wife, and Shaheen Khan and Kriss Dosanjh are amusing and sympathetic as the parents of the bride.

But you keep thinking that Britain has changed more than an updated version of this material could ever reflect.And the question arises: would the National Theatre have dreamt of reviving the original play?

'Elling' to 2 June (020-7610 4224); 'Rafta, Rafta' to 23 June (020-7452 3000)