Defictionalization: The Il Tempo Gigante would go on to be built true to scale in real life. So powerful and noisy is it that it violates the European auto regulations, so it's only allowed on closed circuits (the official top speed recorded is 180 km/h, or 111 mph). To date, it stands proudly on display at the Hunderfossen theme park in Lillehammer.
The Other Darrin: Envoked by necessity in the two follow-up movies, as the old voice-actors had either died or got too old to reprise their parts. Solan has a different voice for each of the three movies. The voice-actors for Ludvig, Reodor, Blodstrupmoen and a few others reprised their roles for Gurin med Reverompa, but in Jul i Flåklypa there is an entirely new voice cast (though Thoralv Maurstad, who voiced Ludvig in the two earlier movies does have a role in the movie, as the narrator).