The shaggy poodle-bobtail mix Willy Wuff rescues two small puppies and ends up with them involuntarily in a mountain hut. Thomas also wants to spend Christmas there with his wife Hilde, his future wife Geli and his seven-year-old son Michael. The constant quarrels between the adults make things difficult for Michael until he discovers Willy and the puppies. The boy lovingly begins to look after the dogs.

Promenade mixer Willy travels to Munich by train as a stowaway. On the way, he meets little Natalie and makes friends with the girl. When he arrives in Munich, Willy is not only hungry but also has to read about a dangerous gang of dog catchers. Willy is happy when he meets Natalie again and is allowed to come home with her. However, Lord, his new girlfriend's distinguished pedigree dog, makes life difficult for him there. When Lord is caught by the dog catchers, Willy doesn't hesitate for a second to help him. In the end, the brave mongrel falls into the clutches of the criminals himself.

Christmas is just around the corner, but Lieschen has nothing to look forward to. Unless a miracle happens, she will once again spend the festive season with her sister Mechthild in the orphanage. Lieschen's heart's desire: Christmas Eve in the bosom of a real family. When she runs away, she meets the stray Willy Wuff and makes friends with him. On their forays through the winter forest, the two discover a count's estate and are given a warm welcome. But there is no sign of the Christmas spirit here, an impending wedding is causing great confusion and the festival of love seems to be having no effect. Can Willy and Lieschen save Christmas and bring everyone's hearts together? Will Lieschen's great wish come true?

Willy Wuff receives the news that his brother Rocco, star of a dog show on the vacation island of Fuerteventura, has disappeared without a trace. The brave four-legged friend immediately rushes to the airport and travels to the Canary Islands as a stowaway. There he meets little Andi, who is terrified that his parents are separating. Willy Wuff not only manages to track down his brother, but also to save Andi's parents' marriage.

Little Kati lives with her mother Anna in a tiny apartment. The two of them are struggling to make ends meet by singing at the Christmas market. When Anna is once again late with the rent, her heartless landlord throws her out just before Christmas. Fortunately, Willy Wuff has heard about their misfortune and rushes to help. He puts them up in the villa of millionaire Jakob, who is on a winter vacation with his mistress. However, when he breaks off the vacation in an argument and returns home, he realizes who has taken up residence in his house. And Kati and her mother mistake the intruder for a burglar. The beginning of a series of amusing mix-ups.