Asterix and the Class Act has a short story "Chanticleerix the Gaulish Cockerel" which Dogmatix, Obelix's faithful pet, costars in. The notes accompanying the story is very interesting: "The idea for this story came from a projected film spin-off. With Rene Goscinny, Albert Uderzo once planned a pilot for an animated cartoon film starring Dogmatix - a rarity which has remained unknown".

This is all we know about the film, but it is likely the Dogmatix series of books contained plot ideas from the proposed movie.