Biden admits his crush on spy pin-up Anna Chapman

The Obama administration closed the chapter on the arrest of the Russian spy ring in what seemed like the most appropriate way: with a gag on a late-night comedy show.

After the 10 "sleeper" agents were handed back to the Russians in exchange for four US spies held in Russia, Vice-President Joe Biden was quipping about the photogenic Anna Chapman, 28 – born Anna Kushchenko – whose exploits had been the fodder for breathless tabloid pieces since the scandal broke late last month.

Jay Leno, the host of NBC's Tonight Show, asked Mr Biden: "Are our spies this hot?" And the Vice-President, taking a mock serious tone, replied: "Let me be clear. It was not my idea to send her back."

Ms Chapman, who had claimed to be running a successful property website, became the pin-up of the group, thanks to sultry photos culled from her social networking profiles and the decision of her British ex-husband, Alex Chapman, to sell his story to the tabloids. With tales of messages written in invisible ink and money buried at secret locations, the story had all the hallmarks of a traditional spy novel, but without any actual state secrets having been found out or passed on. The apparent ineptitude of the spy ring became the staple of the late-night comedy show routines for more than a week.

The 10 were swapped for four US agents on Friday, shortly before Mr Biden taped his Tonight Show appearance. He was asked if the four-for-10 swap was a fair deal.

"We got back four really good ones," he said. "And the 10, they've been here a long time, but they hadn't done much." And then, referring to the right-wing talk show host, Mr Biden added: "I thought they'd take Rush Limbaugh."

Eric Holder, the US Attorney General called the swap "an opportunity to get back four people in whom we have a great deal of interest". He also gave new information on the seven children of the Russian agents, saying they all were allowed to return to Russia "consistent with their parents' wishes".

The wit and wisdom of the vice president

'Chuck, stand up, let the people see you!' - Joe Biden to wheelchair-bound State Senator Chuck Graham while on the campaign trail in 2008.

'I mean, you got the first mainstream African-American who is articulate and bright and clean and a nice-looking guy. I mean, that's a storybook, man.' - Mr Biden on Mr Obama, quoted in The New York Observer in January 2007 during the presidential campaign.

'Mr President, you're the guy that made it happen – this is a big fucking deal!' - Mr Biden's aside – intended for Mr Obama only – is picked up by press microphones at a White House ceremony to announce Mr Obama's health reforms in March.

'Why don't you say something nice instead of being a smartass all the time?' - Mr Biden to a shopkeeper who offered him a free dessert if he lowered taxes.

'God rest her soul.' - Mr Biden, speaking at this year's St Patrick's Day celebration at the White House, on the mother of Irish Prime Minister Brian Cowen. Mrs Cowen is still alive. When he learned of his error, Mr Biden reflected, "a silent mouth is sweet to hear", and left the podium.