Lasse recurs within the wild goose flock led by Akka, accompanying Nils and Morten on their journey across Sweden. He is a male goose defined by his substantial appetite, often consuming large quantities of food.

This notable appetite fuels his portrayal as a source of light-hearted humor within the flock's dynamics. Lasse develops a romantic interest in another goose, Suirii, recognized for her distinctive high-pitched singing voice that other characters find irritating. Their relationship advances, culminating in marriage during the migration journey.

Following the marriage, another goose named Gusta begins teasing Lasse, indicating ongoing social interactions and potential tensions within the group. Lasse participates fully in the migration from southern Sweden to Lapland and back, experiencing the various adventures and challenges the group encounters throughout the journey.

His role remains consistent as part of the ensemble cast of geese, contributing to group dynamics without significant individual story arcs beyond his established traits and relationships.