The Pony Wagon

A horse-drawn, four-wheeled wagon, gaudily decorated with bright colours and tinsel, traditionally lit with lanterns. The wagon has a driver, a robed and crowned man called 'the King', a bard, and an enormous quantity of sweets. The arrival of the Pony Wagon at dusk on Pony Night signals the start of festivities for the children of Duntown. Many families have a tradition of following the Pony Wagon through their neighbourhood. 
Nowadays, most parts of the city have their own Pony Wagon, as Duntown is now so large that it is unfeasible for the King and his wagon to reach all parts of the city in a timely fashion. Once a circuit of their neighbourhood has been completed, the King and his entourage continue on to the Temple of Dendrah - Duntown, where the procession ends with all Pony Wagons meeting in front of the Temple.
This has given rise to an annual competition for the best Pony Wagon of the Year, judged by representatives of each council area. As each has one vote, and will vote for their own neighborhood regardless of merit, each can (and does) claim victory annually.

Propulsion

The wagon is dragged by horses, and not ponies, despite the name. The wheels are never spoked and are instead made of solid pieces of wood. The reason for this has been forgotten, and no one in Duntown is exactly sure why ponies are not used.
We can surmise, however, that the ritual is of foreign origin, because horses do not live in Westlo and were introduced with the first humanfolk around 800 years ago.

Additional & auxiliary systems

Some examples of the Pony Wagon have automated, or semi-automated, sweetie cannons. These allow large quantities of sweeties to be distributed to the people on the street.
(Semi-automated sweetie cannons are actually just children throwing things out of a hole.)