Viewers would be ill-advised not to take this parody fairly seriously, especially given the remarkable insights provided by the director's surprisingly modest commentary.
In this commentary (available on the DVD), director van Bavel seemed to believe 'a' major defect in the movie is that of Redboy's changing age, necessitated by the fact that the filming took longer than originally anticipated. Perhaps the depth of this issue can be illustrative of the complex art of this marvelously silly parody of films and life.
Yes, at first the viewer wonders if there are two actors. But by the end of the movie, it becomes apparent that this is not a negative at all -- on the contrary.
This is a film with binary themes related to the protagonist: studentsuper spy, toysreal weapons, the imaginarythe real, the childthe man. When I saw that the childman theme was so important (the child-warrior theme being an archetypal theme in literature, viz. Joan of Arc, King Arthur, etc.), I began to see that presenting Redboy as of an ambiguous age, first young, then unpredictably older, is certainly one of the greatest and most perceptive strengths of the film, if not the greatest strength. Children, after all, may at first seem incapable, then surprisingly prove to be masters of their situation. The discontinuity of Redboy's age forces the viewer to confront a truth of humanity that can never be so graphically reflected in real life.
Up to now, perhaps only novels have been able to portray characters over a span of time -- or, in film, the comparatively artificial use of several actors to portray one character. It may in fact be that few movies in history have provided us the opportunity to see the protagonist over a wider variation in age and appearance, since, as van Bavel notes, children that age change rapidly.
Granted, if van Bavel had known from the beginning what the filming situation was to be, he almost certainly would have planned things differently -- even if he had in fact made the decision to include scenes from several divergent ages over a couple of years for Redboy. But as it is, I can't imagine apologizing for the fact that Redboy is of varying ages in the film, at least not without major qualification, even if in fact it seemed an accidental development. In fact, as well all know, art is characteristically 'accidental' -- or seems to be at the time. The fact that van Bavel didn't scrap it or re-do the whole thing with another actor is also an artistic decision.
Now, I'm aware, as van Bavel suggests in the commentary, that there is a danger of reading into the film more than is there, but as I say, even if the age issue was unplanned, that does not make it any less valid a strength, and I wouldn't wonder if it is not, consciously or unconsciously, one of the reasons for the admirable success of the film.
Review by Jasha Hirsh from the Internet Movie Database.