Charlie Sheen: Rogue male is simply irreplaceable

Ashton Kutcher, whose finest moments up to now have been uttering "Dude, it's a llama!" in the lamentable Dude, Where's My Car? and saying "I do" to Demi Moore, takes on the unenviable role of Walden Schmidt, a recently divorced internet tycoon in the latest (gallingly the ninth) season of CBS's Two and a Half Men. The dashing 33-year-old is, of course, replacing (the quite possibly irreplaceable) Charlie Sheen who played the hedonistic jingle writer Charlie Harper ("Everybody's got a little baggage... I drink and try to mouth-kiss hookers") in this wildly successful US sitcom, created by Chuck Lorre and Lee Aronsohn; at its height the show attracted more than nine million viewers and The New York Times somewhat hysterically called it "the biggest hit comedy of the past decade".

Sheen, who was reportedly earning $1.78m per episode on TAAHM at one point, was sacked after unhinged pearls such as this about his old boss, Lorre: "I wish him nothing but pain in his silly travels especially if they wind up in my octagon. Clearly I have defeated this earthworm with my words – imagine what I would have done with my fire-breathing fists." He also called his TAAHM co-star Jon Cryer (memorably Duckie in Pretty in Pink) "a turncoat, a traitor, [and] a troll". Sheen was, not unreasonably, fired in March this year and his character bumped off.

Enter Ashton Kutcher who is, frankly, on a hiding to nothing. He's gamely maintained that "I can't replace Charlie Sheen but I'm going to work my ass off to entertain the hell out of people!" But this staggeringly ordinary (and oddly comforting) comedy only really worked at all because of Sheen's hell-raising reputation. And when the main attraction leaves a TV show, it's fatal. The "replacement turn" hardly ever pans out; invariably they leave the loyal viewers craving for the original main draw.

David Duchovny's absence from The X Files – his character Fox Mulder was abducted by aliens – was a disaster for Chris Carter's sci-fi show. While Robert Patrick tried his darndest as the replacement hero, the dogged John Doggett, there wasn't (how could there be?) the chemistry Duchovny had with Gillian Anderson's Dana Scully. Once Duchovny lost interest, in was time to pull the plug. Similarly, ITV's ludicrous Midsomer Murders has never recovered from the departure of its star, John Nettles. Neil Dudgeon is an accomplished actor, but the crime series was Nettles's Tom Barnaby. It's like Inspector Morse without John Thaw, or Prime Suspect without Helen Mirren. It simply doesn't work. It's best to create a spin-off series, which also rarely works. And the fact that ITV's Taggart was still called Taggart after Mark McManus (who played Jim Taggart) died in 1994 was frankly surreal. Call it something else.

Soap operas circumnavigate an actor leaving the show by simply keeping the character and plonking another actor in their place, hoping we won't notice. It's insulting. Much like the silly hiatus caused when Barbara Bel Geddes left the Miss Ellie role in Dallas for a year, to be replaced by Donna Reed. And, of course, it never recovered from the death of Bobby Ewing (Patrick Duffy). So, disastrously, they brought the character back, in the shower; thus the whole last series was a "dream". And even the exquisite Mad Men suffered from the absence (for several episodes) of Christina Hendricks's Joan in series three.

Australian soaps are also serial offenders: there have been three Lucy Robinsons (Kyle Flinker, Sasha Close and Melissa Bell) in Neighbours and two Pippa Routledges (first played by Vanessa Downing, then Debra Lawrance) on Home and Away. While on EastEnders there have been three Janine Butchers – Rebecca Michael, Alexia Demetriou and the current Janine, Charlie Brooks. I'd mention the replacement of Josie Jump in CBeebies' Balamory but that might appear petty.

Good luck to Kutcher tonight, but you can't really see the show working as well as Cryer (uptight, neurotic) and Sheen's odd-couple brothers. Best to stop or make "One and a Half Men".

'Two and a Half Men' is on tonight at 9pm on Comedy Central