St. Nikolaus is coming to town to bring treats and favor to the good boys and girls. This figure stays pretty much constant, but has a different sidekick depending where you live. Most companions are a little bit scary, sorta threatening, and generally displeasing to kids. There is also the very controversial sidekick in the Netherlands, Zwart Piet.
In the Netherlands, Sint Nicolaas or Sinterklaas is said to be a saint from Spain. Each year he comes to the Netherlands by boat to celebrate his birthday on December 5th. He celebrates by giving away presents to obedient children, and possibly punishing the bad ones, some of which, are taken to Spain to never return to their families. Sinterklaas has many helpers, which are known as Zwarte Pieten.
Zwarte Piet translates to Black Pete or Black Peter and is a companion to Sinterklas, or Saint Nikolaus. The character first appeared in an 1845 story, "Saint Nicholas and his Servant" by Amsterdam schoolteacher Jan Schenkman. In this story, Sinterklaas arrives by steamship, bringing with him a black helper. This story was so popular that the helper was included into the Dutch Christmas festivities.
Zwarte Piet was an unintelligent black man whose job it was to scare children into obedience. The good children were given sweets and presents, while the naughty kids would be given salt if they were lucky. Zwarte Piet was also known to give children spankings who were naughty or hit them with sticks, which he carried in a bag. That bag could also be used to stuff children into and bring them to Spain. Those children were then trained to be Zwarte Pieten. This tradition has changed quite a bit. Traditionally, Zwarte Piet is black because he is a Moor from Spain. Others insist that he is black from the soot after coming down the chimney. Either way, those portraying the character paint their faces black, wear colorful Renaissance attire, curly wigs, large earrings and bright red lipstick. Today, Sinterklaas has a lot more helpers now. Black Pete has lost his speech impediment, and is a lot more friendly towards children. He now entertains them and charms them with cookies and sweets. Despite being a very controversial character among other nations, the tradition of Black Peter is very much still alive in the Netherlands.
Here are some additional sidekicks of St. Nick that you may run across depending on where you live.