Knickerbocker Glory

The dessert Knickerbocker glory is a splendid British treat comprised of crushed raspberries, vanilla ice cream, and topped with cookies. The exorbitantly spoiled Dudley complained about the quantity he had received in what was his second ice cream treat of the day, and convinced his father to buy him an entirely new glass. Harry, to his disbelief, received the one Dudley was so keen to reject. 

This came after an unprecedented series of lucky events that put Harry in a happy disposition. It was short lived as an unexpected turn of events unfolded. However it is the opinion of the Trolley Witch's that the unexpected should be most expected when you have an unknowing wizard hardly more than chaperoned by the mugglist of Muggles. 

And so it was that while Harry was experiencing one of the best mornings he had witnessed in quite a while he was also about to experience one of his worst in at least as long. His interactions with the snake so enraged Uncle Vernon he could hardly speak and earned Harry "his longest-ever punishment. By the time he was allowed out of the cupboard again, the summer holiday had started..."

This pattern of good that gets even better, only to com crashing down again to a new low,  foreshadows Harry's life at Howgwarts. Not long after he emerges from the cupboard after his worst punishment to date is when the first Hogwarts letter arrives. Although Harry doesn't understand it's significance at the time, or for yet a bit after it's arrival, it signals another positive in his life once he is able to get through the Durselys trite negativity.