Chris O'Dowd

Ever considered the erotic potential of a barista's frothy coffee machine? Since the hopelessly inept IT department first flickered into life in this peerless comedy, the world has moved on. Back in 2006, the careers of Chris O'Dowd, Richard Ayoade and Katherine Parkinson were just booting up. And the all-pervading influence of the internet was still cranking up. But now, as the trio log in for this last-ever one-off special - featuring a spooky guest turn from Noel Fielding - the faces of Roy, Moss and Jen are famous, and there's a glint of the Black Mirror about the tangles they get into as viral videos, micro-bloggers and hactivists up the levels of paranoia.

Those familiar with Graham Linehan's hyperactive Twitter presence will be unsurprised by some of the subjects tackled in this the hour-long finale of his geeky, live audience sitcom: embarrassing viral videos, anonymous hacktivists, the NSA. It's a testament to his fine plotting skills and mastery of tone that such dark fare is seamlessly woven into the shows usual cartoonish set pieces and Seinfeldian verbal tics ('small-person racist', 'emotionally artistic').

Along the way, our hapless trio of Moss (Richard Ayoade, whose new film The Double features original Reynholm Industries head honcho Chris Morris, fact fans), Roy (Chris O'Dowd, fresh from BBC2's Family Tree) and Jen (Katherine Parkinson, thankfully less shrill than in previous series) do battle with tiny baristas, pepper spray, women's slacks and, er, a van with breasts.

Naturally there are plenty of laughs to be had, especially from Matt Berry, on gloriously silly form as lunatic boss Douglas Reynholm.

But it drags in places and the same old problem remains: the main characters elicit no warmth. As a result, when the IT Crowd depart their basement lair for the last time this viewer was left feeling strangely unmoved. Adios then, nerdlingers: gone neither with a big bang nor a whimper.

The IT Crowd returns for a one-off special which will most likely be its last ever (since Richard Ayoade is now a director and Chris O'Dowd is Hollywood's most unlikely heartthrob). Despite repeated attempts, I've never managed to find it even the slightest bit amusing - its strained "aren't geeks weird!" jokes and broad performances, accompanied by gales of studio audience laughter, just aren't for me. But for those who have enjoyed the previous four series, the special offers more of the same, wisely keeping to the same basic premise (and basement) rather than sending them all on holiday or something.

It's been a rum little monkey, Family Tree (BBC Two), full of bad jokes and oddball characters.

But, as Chris O'Dowd's Tom Chadwick dithered over his future in a 'there must be a series two'-type cliffhanger, there was a surprising melancholy to waving farewell to this curious bunch at the airport.

The satire on the whole Who Do You Think You Are? TV franchise was a tad overcooked - surprisingly so, given the pedigree of writer/director Christopher Guest - but there was just enough wit scattered among the branches of Tom's extended clan to make up for the feeling that no family could contain this many nutters.

'Do you find that being around books makes you more clever?' Tom asked potential squeeze Ally. 'No, it makes me feel like all the ideas have been written already,' she replied. They were made for each other.

And Fred Willard's Al Chadwick had a camp hoot with a stream of bad gay jokes. 'How do you fit four gay men on one bar stool?... turn it upside down!' So wrong.

Tom (Chris O'Dowd) is still in California with his new-found relatives in Christopher Guest's transatlantic mockumentary. The Chadwick clan's investigation into why their ancestor Charles fought for both sides during the American civil war is punctuated by Tom's startled amusement at his extended family's pasted-on quirks, because why bother with actual personalities when you can give your characters a gently eccentric passion for historical re-enactments (or conspiracy theories, or owls) instead?

This is a hit-and-miss sort of sitcom at the best of times; this week it becomes predictable in the wrong way. When we hear that our hero Tom's great-aunt left her home to a female friend, we wonder if they were actually more than friends, but Tom's dozy friend Pete takes ages to twig. Also, one minor character is a gym owner whose West Indian patois is hard to understand: isn't that the kind of joke the series mocks in its 1970s sitcom pastiches? Anyway, Chris O'Dowd is still good as Tom and has a nice monologue about being single.

With star Chris O'Dowd and This is Spinal Tap creator Christopher Guest attached, there has understandably been quite a bit of hype and expectation surrounding this new comedy series. Thankfully, three episodes in and that hype is looking increasingly justified.

It's difficult not to draw comparisons to the creator's previous comedy ventures: while some of the gags are groaningly predictable (as when cocky Pete is pitted against a small child in the boxing ring - what could possibly happen?), the very best jokes in the series are the deadpan, subtle 'did I just hear that' variety that made ...Spinal Tap so funny. Tom's ventriloquist sister Bea (Nina Conti) is particularly hilarious, her id-outlet monkey hand puppet sharp, rude and wonderfully weird. Their appearance this week as wedding entertainment is predictably disastrous.

Meanwhile, this episode takes Tom's bittersweet - and rather hopeless - search for his family history into the world of sport after he makes another discovery. Hopefully those discoveries will keep on coming as this is getting better by the week.

There's another lovingly detailed pastiche of a 1970s sitcom right at the start of tonight's episode. Tom (Chris O'Dowd) visits his father to show him the photo of their ancestor, but first has to distract him from watching DVDs of his beloved Move Along Please!, a police station comedy that's a sort of Carry On version of The Thin Blue Line ("Well you said you wanted us to make a big bust this week, Sergeant!").

It's one of many lovely touches in a comedy that looks like being a grower. The slightly dopey Tom has embarked on a genealogical quest that takes him to a theatre in Hove, where the over-reverent historian ("I look on the theatre as like a temple...") is beautifully played by Hugh Sachs from Benidorm.

It turns out Tom's great-grandfather was an actor - and he played opposite Laurence Olivier, no less.

In the new sitcom Family Tree, Eeyore-faced Chris O'Dowd plays Tom Chadwick, a recently cuckolded, jobless single who's inherited an old photo of someone he believes to be his great-grandfather. Tom embarks on a search to know more about his ancestors, discovering ever more exotic and esoteric branches of his genealogy. He's accompanied by his hapless pal Pete and sister Bea (the ventriloquist Nina Conti), who, due to a traumatic childhood incident in a zoo, now voices her more unorthodox opinions via a hand puppet called Monkey.

This is a very funny comedy and, watching preview episodes on my computer with headphones on, I chortled out loud about six times (a risky thing to do when colleagues all around are ploughing through an Ed Miliband speech). The series is a send-up of kin-hunting series such as Who Do You Think You Are? and Long Lost Family, and because tracking down one's forebears could lead to just about anything, both possibility and improbability are built in. As a documentary spoof, it's more farcical and less 'realistic' than, say, The Office. Nobody really questions the presence of Monkey.

Conscious of its own meta-ness, the show makes fun of different genres, often via its characters watching telly or DVDs, so we get treated to snippets of a mock BBC2 historical soap, or a cringe-inducing flashback to a 70s sitcom. One thing about these TV-within-TV moments, though. It's become increasingly the done thing, in our overly politically correct times, for hip, knowing comedies to get safe laughs by showing terribly un-PC things via the filter of a terribly un-PC character (in this case, Tom's dad). We're supposed to be laughing at, not with, the character. In reality, of course, we're doing both. I find the PC brigade tedious in the extreme, but it seems to me that, if you believe one shouldn't depict Indians with waggly heads, then don't depict them, full-stop. You can't poke fun by proxy. That's having your gluten-free cake and eating it too.

Co-written and directed by Christopher Guest, pioneer of the mock-documentary format, Family Tree stars Chris O'Dowd as a man intent on tracing his family history.

The performances are naturalistic, the pace leisurely, the humour gentle, the focus meandering and the format flexible enough to include mock-doc TV interviews - despite it not being set up as a documentary - and for Nina Conti, who plays O'Dowd's sister, to employ her ventriloquist puppet monkey as a co-star.

The show is amiable, entertaining, whimsical and intriguing, but - a terrific blind date scene notwithstanding - it doesn't seem that bothered about being funny.