In Grou the traditional Dutch Saint Nicolas feast is not celebrated; in this village, people celebrate Sint Piter (Saint Peter) on February 21. For outsiders it looks like Saint Nicolas, but Sint Piter is not of the same origin. On the Saturday before February 21, Sint Piter arrives in Grou by boat. He wears a white cloak and rides a (black) Frisian horse. Sint Piter is received by the mayor and sung to. Subsequently Sint Piter passes through the village in a parade, with the mayor, representatives of committees and school children. Sint Piter visits schools in Grou, the nursery, the care centre, an welcome party for children, an informal reception for the residents of Grou and former inhabitants and sick children. As of 1951 a Sint Piter fairytale has been performed each year. The fairytale is one of the cornerstones of the current celebration and is done in Frisian. Sint Piter songs in the Frisian language are another element of the feast. Since 2021, Sint Peter is accompanied by his companion 'Aldemar'.
Aldemar is a 'creature of nature' who lives in a treehouse with his parents down in the National Parc Alde Feanen near Grou. He wears a half-high hat with welding goggles. On his back he carries a basket which contains 'pipernuts', presents and his iPad.
Several weeks before the arrival of Sint Piter the Sint Piterfrouljuskomitee (Sint Piter women committee) organises a Sint Piter fair. This marks the beginning of the activities of the local entrepreneurs. The revenues, which are always considerable, are used for the performance of the fairytale, publishing books and for Sint Piter games for the children.
During the fair Aldemar is present to take in shoes and boots from small children. These shoes and boots, filled with a present, can be searched for later on in the window of one of the shops in Grou.
On February 21, by the end of the afternoon, Sint Piter and Aldemar are said goodbye in the centre of the village.