And my next guest is...Tony Blair - Stars on the couch

The PM's appearance on Parky is destined to join the pantheon of unforgettable chat-show moments. Adrian Turpin presses the rewind button on the TV format that refuses to die

A for Alan Partridge, the fictional chat-show host whose greatest moment was his revenge on a boy genius who taunted him for not knowing Russian or how to play chess. Partridge: "Have you got any pubic hair?" Fisher: "No I haven't, because I'm nine." Partridge: "I'm 37 and I've got plenty." If only real chat shows were like that (see B).

B for boy genius. Terry Wogan has interviewed many celebrities, such as Madonna, but none gave him as much trouble as 10-year-old James Harries, who went on Wogan in 1988 after opening a Cardiff antiques shop. It was car-crash TV. Asked why he wouldn't go to a normal school, the bow-tie wearing, mop-headed boy wonder replied: "I won't! I won't! Because, they're not ladies and gentlemen, and the teachers aren't ladies and gentlemen, and you wouldn't know anyway because you weren't there, Wogan!" Harries' family had more degrees than the Arctic Circle. Unfortunately, most were bought from the US or awarded by the Cardiff College of Humanities - proprietor one Mark Harries, owner of a local kissogram business and James's dad. Mark was later jailed for burning down a shop he owned, while James had a sex change in 2001.

C for Charlotte Church. The "voice of an angel" is recording a chat-show pilot for Channel 4. Shouldn't be hard to nail down that Gavin Henson interview.

D for drink. Michael Aspel gets Ollied: "Oliver Reed joined us, I heard some uncertain footsteps and he lurched on, waving a jug of orange juice, which was not the drink he had obviously been consuming in huge quantities. He was so rip-roaring drunk that he made newspaper headlines the next day. The front page of The Sun carried a picture of him, mouth wide open, eyes rolling. Apparently a lot of people were outraged ... but as one critic pointed out, it would have been more extraordinary if he'd behaved like a bank manager."

E for Emu. Most people remember the feathered pest's 1976 attack on Michael Parkinson. Some may even know that he went for guest Billy Connolly ("I'll break your neck and his bloody arm," the unamused comic is said to have threatened). Few, however, remember that Rod Hull had launched a similar assault on Noel Edmonds several weeks earlier. Ah, those were the days of public service television. Parky has made a second career out of complaining about Emu - consigning it to the flames on Room 101 and so on - but it didn't stop him from filming a snack commercial with the bird or appearing on Emu TV (see also P).

F for Fergie. The Duchess of York became the first royal to have a chat show when she signed up to Sky a few years ago. As she pursues a TV career in America she has taken lessons from chat-show royalty in the form of Michael Parkinson.

G is for green room. By sticking a camera backstage, Jonathan Ross has created moments of sublime comedy. The look on Martin Scorsese's face in 2004 as he tried to work out who his fellow guests Cilla Black and Johnny Vegas were was priceless.

H for hard sell. Or should that be easy sell? The classic of the genre was Bruce Willis, Sylvester Stallone and Arnold Schwarzenegger's 45-minute plug for the Planet Hollywood restaurant on a 1993 edition of Aspel and Company. The regulators complained, and PR Matthew Freud's career went into orbit. One good thing came of it: Aspel vowed he would never do another chat show.

I for Icke. Never mind the conspiracy theorist David Icke calling himself "son of the Godhead" on Wogan in 1991 - what was that turquoise shellsuit all about? "The best way of removing negativity is to laugh and be joyous, Terry," the former BBC sports presenter said after declaring that 12ft lizards ruled the world. "But they're laughing at you. They're not laughing with you," Wogan replied.

J for joke. Not advisable with the Bee Gees. On a 1997 edition of Clive Anderson All Talk, the brothers Gibb foolishly told the host that they had thought about calling the band Les Tosseurs. "You'll always be tossers to me," quipped Anderson, provoking the brothers into one of the great chat-show walkouts (see also U).

K for killed. RIP Channel 4's Gaby Roslin show, gone but not ... well actually, both, gone and forgotten.

L for long-runner. Gay Byrne's 37 years as host of Ireland's The Late Late Show seems unlikely to be beaten. Byrne is often described as the man who "brought sex to Ireland" through his show. Unfortunately, he was also largely responsible for bringing Westlife to public attention.

M for Marianne. The mythic symbol of the French Republic is currently modelled on the French chat-show host Evelyne Thomas. That's like putting Parkinson on the banknotes. Weird

N for Nigella. One reviewer said of her ITV vehicle: "She gazes at the camera like a tranquilliser-addicted housewife with a glazed grin as she used to remember who she was long, long ago. Done out in a red cardigan over a mumsy turquoise dress" - alarming echoes of Icke - "she looks like your insane aunt who's come to stay for a few days after her latest nervous breakdown."

O for Osbournes. Sharon and Ozzy have been signed up by ITV to rival Richard and Judy. O is also for obscenity. Mrs Osbourne's US daytime chat show was axed after one series, after she asked a New Zealand actor whether he had ever had sex with a sheep.

P for Parkinson. Parky may be sycophantic and self-regarding by turns, but nobody is more insightful about the nature of the chat-show genre. "The notion of the interrogator who puts the fear of death into people and forces life or death confessions is bullshit," he has said. "The only people who have ever cried on my show have been people who wanted to cry ... That might not be in their mind when they come on, but it's certainly in their subconscious. So get rid of the notion of this terrible or very skilled person who can break you down. How could it be that in a situation as artificially contrived as a television studio, you could get this frank and free discussion between two people?"

Q for questions. Not as easy as it looks. Interviewing Kirk Douglas on the BBC chat show Where Do I Sit? in 1971, the comedian Peter Cook tried to ask: "How are you?" but instead came out with "Who are you?" The series was binned after just three shows.

R for rabbit. Essential for the job. But was it necessary to get the Watership Down author Richard Adams to stand in for Wogan?

S for sulk. As practised by Meg Ryan, who declined to answer Parky's questions and then insisted that he "close the interview".

T for tantrums. Russell Crowe insisting on being interviewed solo for a Parkinson Down Under special that also featured Cate Blanchett and Kylie Minogue, causing maximus irritation.

U for uncomfortable. Hard to beat Matthew Kelly confronting Frank Skinner in 2003 about jokes he'd made after Kelly had been falsely accused of child sex abuse. "You and David Baddiel did a show and you did some pretty horrible gags about me. Would you do it now with me sitting here? Are you proud of those gags?" The comedian's "just doing my job" defence couldn't hide the squirm.

V for violence. A recent poll declared that Grace Jones slapping Russell Harty live on air in 1981 was the most shocking chat-show moment.

W for Harold Wilson. Tony Blair is to appear on the new series of Parkinson. But the former Labour prime minister Harold Wilson went one better after retiring from politics, briefly hosting his own BBC2 chat show in 1979. The result was subsequently included in Channel 4's 100 Greatest TV Moments from Hell. Part of the problem, according to the producer Iain Johnstone, was that Wilson's memory was already deserting him. "I said after rehearsal,'We'll do the show at 7 o'clock' and he said, "haven't we just done it?" W is also, of course, for Ross.

X for X-rated. Bill Grundy's 1976 encounter with the punk rock group the Sex Pistols remains one of the most surreal - certainly the most self-destructive - moments in chat-show history. Grundy trying to look insouciant but clearly rattled: "Say something outrageous." Steve Jones: "You dirty bastard!" Grundy: "Go on, again." Jones: "You dirty fucker!" Grundy: "What a clever boy!" Jones: "What a fucking rotter." Grundy: "Well, that's it for tonight." The veteran interviewer's career never recovered.

Y for Yates, Paula. Some shows are live, others recorded. But it took Channel 4's Sex with Paula celebrity chat show a whole nine years to reach the screen for fear she was promoting promiscuity. Hope it wasn't made by the current affairs department ...

Zzzz for Davina. And if you don't believe me, take a look at the ratings - down a quarter after one week.