The mood of Parliament's debating chamber can change in an instant as MPs compete to expose the biggest blunders, the widest inconsistencies, the sharpest u-turns and the most telling lies.

Then there are the bad days.

Yesterday began moderately as Labour deputy leader Annette King attempted to embarrass Prime Minister John Key over Finance Minister Bill English's speculation about the possible sale of Kiwibank.

A mildly irritated Key snapped: "The Minister of Finance is a Minister of the Crown and not a toddler. I do not force him to ask me what questions he is allowed to answer in public. If he gets asked a question, I expect him to answer it."

The irritation level went up a gear with her next question, needling Key both about something English said of him a long time ago and about his own aptitude for making news that goes global, most recently his vasectomy.

King: "Was Bill English correct when he said that John Key just bounces from one cloud to another and does that account for the international media reporting his antics in the 'odd-spots' of the newspapers, including his comments about being eaten by Tuhoe, his vasectomy, his standup routine on The Late Show with David Letterman, and his waterbed policy?"

The "waterbed" referred to Key's so-called explanation of Whanau Ora a few months ago in terms of the relative water levels in a waterbed.

Key stayed on until later in question time when Labour's mafia, Pete Hodgson and Trevor Mallard, quizzed him more about a blind trust that appears to come with a braille translation.

But the PM clearly has advice that, not being the legal beneficiary of the trust or company in question, he has no ministerial responsibility and won't be answering questions any more.

Having dealt to Labour, Key departed, leaving Building Minister Maurice Williamson to answer patsy questions about the warm reception for the latest leaky homes package.

Labour's Phil Twyford was challenging Williamson over parts of the package when suddenly attention turned to the public galleries, where a group of 13 beauty queens, contestants in the Miss Universe contest on Saturday, made their entrance, all sashed up.

The mongrel in Mallard instantly turned to pup and he took a point of order suggesting it was usual for visitors to the gallery to be introduced. The House stood and applauded, and the ladies waved back.

Williamson, it turned out, had entertained the young women in his office at lunchtime, giving his 945th demonstration of his iPad.

Lest anyone think his motives were not political, he pointed out that his Pakuranga electorate had been the home of the only New Zealander to win Miss Universe.

Labour's Darren Hughes was mindful that Labour would not want to be seen to be supporting beauty contests while not wanting to appear churlish towards a bunch of happy young things who always tell the judges they love reading and want to end all wars.

So he took his own clever point of order: "I just wanted to assure the guests in the gallery that the Labour Party, too, believes in world peace and we will be joining their crusade in that particular regard."

By now their spell of beauty and goodness had settled across the chamber and Leader of the House Gerry Brownlee stood to let the ladies know that the man who had just sat down was Parliament's most eligible bachelor.

Key missed one of the good times in the House.

But as chance would have it, he bumped into the beauties in the corridors and had his own audience with them.

Bad, good, ugly, beautiful, another day in the House.