opper thinks summer vacation is boring. He misses his father who is sailing the seven seas. He can't figure out Sille who's cute. And his best friend, Viggo, always has to help out his punctilious dad, Mr Lion, in the café on the first floor of the red house where Topper lives on the top floor with his mother. One day, Topper finds a magic pencil and when he draws a rhino on the wall, the drawing comes to life! While Topper and Viggo try to keep the rhino, which they name Otto, well fed with black bread and raspberry soda before it devours all the furniture, Mr Lion pleads with the local authorities to come and remove the stomping pachyderm.

Overview from themoviedb.org