Last Night's TV: Empty, BBC2<br/>That Mitchell and Webb Look, BBC2<br/>The Girls Who Were Found Alive Channel 4

They threw away most of the good stuff

There are so many ways for a sitcom to be bad that it's surprising anything even remotely amusing ever makes it on to the screen. But of all the ways of not being funny, the most dispiriting is Having Your Heart in the Right Place. You may remember All about Me, a Jasper Carrott-Meera Syal vehicle about a multicultural family, narrated by their severely handicapped son. It was as conclusive a demonstration as you could want that the right place for a comedy's heart is in the fridge.

Empty suffers from a similar excess of decent sentiment. The protagonists here are Jacky and Tony (Gregor Fisher and Billy Boyd), whose job is clearing the houses of dead people around Glasgow. As they work, they swap jokes, fantasies, film references and general banter. But, as the title clunkingly hints, the jollity masks the emptiness of their lives. Jacky is sharp-witted and well read, but in late middle age he has accomplished nothing with his life, and his insistence that he is content with his lot doesn't quite square with the eruptions of temper when Tony pushes him on the subject; Tony is younger and would like to make his mark on the world, but while he has time on his side, he knows that he hasn't got the brains.

This is promising. The man whose intelligence doesn't match up to his ambitions is a stock comic character; the man whose ambitions don't match his intelligence is rarer on screen, though depressingly common in real life: is Empty opening up new comic territory? From time to time, Iain Connell and Robert Florence's script gets quite neatly the tone of masculine banter: solidarity built on mutual insult and a code of shared allusions not easily penetrable to interlopers; and you can't hate a comedy that assumes Eric Sykes in The Plank is one of the highlights of our culture. Oh, all right, I can't hate it, you probably can.

With all this going for it, though, Empty doesn't gel. The dialogue and the acting don't settle to a tone, wavering between naturalism – and the absence of a studio audience suggests that's what's being aimed for – and panto-like overemphasis. It may be, too, that stock characters are stock for a reason; perhaps intelligence without ambition can never be as funny as the other way around. Try to imagine Dad's Army with Sergeant Wilson as the main character instead of Captain Mainwaring. I don't think there's any doubt it would have been much feebler stuff. (And who was funnier in The Good Life? Modest Tom Good, or viciously social-climbing Margo Leadbetter?) And any surviving comic possibilities are finished off by the jaunty, folksy guitar music, using the sort of tunes you can imagine accompanying one of the films on the Teletubbies' tummy screens – small children face-painting, that sort of thing. At its worst, the music has a cringe-making literalism. When Jacky and Tony discovered that the bedroom of the house they were emptying was full of model boats, we were treated to a flute-and-guitar rendition of "When the Boat Comes In"; the rest of the time, it signals "Funny!" more blatantly than any laugh track ever could.

Fortunately, if you want to see properly heartless comedy, you can tune in an hour earlier and get The Mitchell and Webb Look, which last night included a particularly nasty sketch about a village-hall panto threatened with censorship by the politically correct brigade on the parish council, who wanted to ban such time-honoured Christmas fare as the dame rape – for which the principal boy wore the traditional strap-on phallus – the dwarf-gassing, and Cinders sucking off the panto horse. Loved it. The series also includes a good running gag about television "documentaries" that show off appalling physical conditions – last week, the Boy with an Arse for a Face; this week, the Woman with the Second Head That Won't Stop Calling Her a Bitch. "Continuing our Point and Laugh but in a Caring Way season...." went the voice-over, before telling us to look out for this on Five. Now, I would associate this genre with Channel 4, which gave us such delights as The Boy Who Gave Birth to His Twin and Born with Two Heads. Then again, Channel 4 also gives us Peep Show, a sitcom that stars David Mitchell and Robert Webb. Not that I'm accusing anybody of anything.

The Girls Who Were Found Alive recounted the case of Lisa Hoodless and Charlene Lunnon, who in January 1999, when they were 10 years old, were abducted while on their way to school in Hastings by a convicted paedophile, Alan Hopkinson. The title gives away the plot, though Charlene, in particular, was traumatised; so was her adoring father, who was subjected to the humiliation of his long-dead past as a junkie and a thief being resurrected by scandal-hungry tabloids. There wasn't nearly enough story here to fill an hour; whether Charlene and Lisa's inspiring assertion that such horrors needn't ruin your life made up for that is a matter of taste.