Well from what I understand all the footage was filmed by a foreign (Japanese I think?) Company that went bankrupt and all the footage was bought by the American company and through narration retconned and edited into a movie. I believe the official story is that it’s the sane dog and cat filmed from birth over three years, but some people are claiming that they killed as many as 20 kittens filming some sections. I don’t want to believe it but I do have to admit watching the movie now there are definitely some questionable moments…