I completely agree. My guess is that Charlie Day came in with a lot of ideas to make his character genuinely funny, and GDT let him do them, so he nearly steals the movie. It doesn't feel "of a piece" with the rest of the film.

I really think that just a little bit of punch-up can change a lackluster script into a fun adventure, but it needs to be applied with an even hand. Imagine if the self-sacrifice scenes--which were great ideas with good actors--had had a little more punch behind them because we liked the characters more. As is was, it involved the two least emotionally accessible characters.