Alternate Character Interpretation: Trent seems to think Gloria not showing up at their wedding means it's just her typical It's All About Me attitude, but CJ says she understands, as Gloria not only said she was happy but even said Trent was quite a catch, approving of their relationship. It's implied Gloria, perhaps for once in her life, realized her selfish, narcissistic attitude would only ruin the happiest day of her daughter's life, so she decided to do the selfless thing for once and not attend. It's not confirmed which of them, if either, is right about her behavior.
Harsher in Hindsight: Hungry's sleepiness and constant hunger stops being cute once it becomes apparent that he wasn't just a lazy Big Eater. He was the runt of the litter. Hungry was sick and dying.
Hilarious in Hindsight: There is in fact a short manga called "Nine Lives" with a similar concept of a cat reincarnating nine times... with lives eight and nine being the same owner. It also has just as much feels.
What Do You Mean, It's Not for Kids?: Just because the book was adapted into a family-friendly movie doesn't mean the book is for kids itself. While not the most graphic book, it has allusions to sex, violence, and death that the movie removed and there's some mild profanity sprinkled about. The sequel book is even more mature, as is its Spiritual SuccessorA Dog's Way Home, with suicidal characters and addiction discussed blatantly. A Dog's Purpose and its sequels have Lighter and Softer books about the protagonist as a puppy.
Films
Critical Dissonance: The film got mixed to average reviews from critics, but audiences loved it, seeing it as a wonderful Tear Jerker film. Fans of the book, however, tend to be split over its quality.
Designated Villain: Brady in the second film doesn't really do anything wrong except not want another dog around (completely reasonable, especially considering that they already have one, not to mention that she didn't even talk to him about it first), complain about Max's campaign of terror against him (also completely reasonable), and make a few snide comments about CJ's non-existent musical career (not reasonable, but even then, it's not outright cruel).
That being said, this is in Max's point of view after finding out Trent is nearby, so really the "villany" is likely a side effect of Max under the Die for Our Ship lens. Said campaign of terror was intentionally meant to make Brady look bad and for CJ to go to Trent instead.
Hilarious in Hindsight: Kirby Howell-Baptiste plays Maya, one of Bailey's owners in his many lives. He helps her find love, serves as emotional support, and romps with her kids. She would later star in The Good Place where her boyfriend thinks of breaking up with her... and considers giving her a puppy to soften the blow.
Moe: Maya is Endearingly Dorky and a sweet dog owner, who trains Tino and seems to read his mind. She's just so darn cute.
Overshadowed by Controversy: Not only is the alleged animal abuse video from TMZ (which showed an apparently terrified dog being made to perform stunts in moving water) the most well-known thing about it, there are probably some who wouldn't have heard of the film without it. It resulted in the film receiving thousands of 1/10 votes on IMDb, before the movie had even been released. It's worth noting that the video of said event is heavily edited, and the people involved in the movie (including the author and director) as well as independent reporters who have viewed the full footage have all stated that the dog was neither harmed or traumatized (the claim is that he'd happily done the stunt several times before, and his hesitation was only due to approaching the pool from a different spot than he was used to). They admitted a mistake was made, but the TMZ video does not give the whole story. Unfortunately, the damage had already been done, and film had the stigma behind it for a good while. Fortunately, it has died down a lot since then.
They Changed It, Now It Sucks!: The film loses a lot of the book's xenofiction elements. Less emphasis is put on the protagonist's POV and more on the humans. As a result, fans of the books tend to have murky receptions about the films.
