New Girl's Nick and Jess are just Ross and Rachel in disguise

Jess (Zooey Deschanel) and Nick (Jake Johnson) in 'New Girl' (2013 Fox Broadcasting Co.)

Cast your mind back to February 1, 1996. Football hadn't yet come home, Dolly the sheep was a biotechnological twinkle in the eye of the Edinburgh Roslin Institute and, for another 12 days, Take That were still together, bashing out the hits without Robbie.

Astonishingly, for people not paying close attention to both the space-time continuum and blockbusting sitcoms, that was also the point where Friends got significantly less good. It was the night, in the US at least, when Ross and Rachel got together in “The One With The Prom Video”, you know the one, “he's her lobster” and all that.

For a long period in my late teens, I was convinced this was the moment Friends stopped being good and made a point of loudly declaring so. Hindsight suggests that that was a spot of intellectual bravado akin to declaring that The Beatles aren't much cop. OK, The Animals, maybe.

Friends remained better than 98 per cent of other American sitcoms of its era (Seinfeld finished in 98; Frasier topped it, despite its own Ross and Rachel moment with Daphne and Niles), but it wasn't quite the same once the Ross-Rachel narrative, which had tied the early episodes together, reached its logical conclusion.

Especially with the writers so frequently having them be off and on and then - spoiler-from-2004 alert! - chickening out and putting them back together for the final episodes.

The lessons learned in series two of Friends still resonate in many US sitcom writing rooms. There's a consensus that having two leads fall in love is vital to keeping viewers interested - not that Seinfeld bothered with that stuff - but it's a consideration that has to be balanced with the American networks' preference for syndication-friendly 24-episode seasons. Do it too early and you've blown your narrative load. Leave it too late and… you've already been cancelled.

That was probably something playing on the mind of Elizabeth Meriwether, creator of New Girl, the Zooey Deschanel-starring hit which returned to E4 on Tuesday for series three. Her Ross and Rachel are Zooey's Jess and Jake Johnson's Nick. She's a slightly dappy school teacher who people think is a bit of a dork (despite looking exactly like the beautiful Zooey Deschanel), he's a hapless loser of a barman (who also happens to be very handsome). Despite that suspension of reality, New Girl has become beloved because, in the main, it's very funny and very cute.

This week's return featured one of my favourite TV moments of the week, a bedraggled Nick trying to convince a young kid in a hotel to give him his all-inclusive wristband by looking to the future: “One day, you're going to meet a girl and you'll really like her and you're going to want to give her everything but you won't be able to afford it because your life's a shambles.” Amen to that.

The series opener hinted in a self-conscious way about the trouble with two of its leads coupling, so maybe they'll make it work. However New Girl deals with it, a dip in the US ratings suggests it may have succumbed to Ross & Rachelism.

Not so for two other long-standing US hits, How I Met Your Mother, which ends its nine-year run on E4 in July, and The US Office, which is equally deep into its final season on Comedy Central. How I Met Your Mother's entire structure was based on a kind of anti-Ross & Rachel-ness. Its set up was pretty similar, three guys, two girls in New York City. But its narrative USP was the fact that an older version of one of the leads, Ted (Josh Radnor), was telling his kids in 2030 how he, well, met their mother. Despite a will-they-won't-they relationship with Robin (Cobie Smulders), we learned the identity of the mother (Cristin Milioti) in the last episode of the penultimate season. The drama of the final season has been how exactly two people whose paths we know cross, cross.

Revelling in playful diddling with narrative structure, Rashomon effects and smart leaps in time, it's been a fitting final season for a show that, despite a heavy E4 presence and a cast that includes a genuine A-lister in Jason Segel, seems to have bobbed along under the radar in the UK.

As has the American adaptation of The Office, which has outlived its British forbear by a mere 187 episodes. Its take on the original's R&R-style romance between Dawn and Tim was the one between their equivalents Pam (Jenna Fischer) and Jim (John Krasinski). Having realised that dragging it out may have tested viewers' patience, the writers paired them off early and then painted them as a boring couple. Of course it helped that The Office had the time, money and talent to build up a fantastic ensemble cast out of whom they were able to build other romances. Now - having paired off several - they're back to Jim and Pam, with Jim having invested their savings in a new sports management company. Will it break them up? Again, another nice reverse of the R&R dilemma, although, unlike How I Met Your Mother, you can guess that it probably won't. He's her lobster.

Grace Dent is away