This is a charming but simple tale of a boy raised by trolls that like to wear, and when alarmed hide in, cardboard boxes. These "boxtrolls" live under the streets of a town called Cheesebridge, where the elite are highly focused on cheese, to the detriment of all else. The trolls are misunderstood by the people up top, the boy doesn't know he's not a troll, and the exterminator has put ambition ahead of morals.
The conversation between Mr Trout and Mr Pickles will likely not register as amusing with kids, but even some of the kids jokes will be amusing to adults.
Winnie Portley-Rind: Did they kill your parents and let you watch? I mean make you watch?
Some gripes: all of the trolls have simple names, like "shoe", and "fish", and some of the humans do (Mr Trout and Mr Pickles), but not all of the humans. I think that would have been fitting to do. The movie is stop-motion animated, but the animation is so slick it is hard to tell that it is not just a CG version of stop-motion animation. There is a sequence in the end credits, featuring a conversation between Mr Trout and Mr Pickles, that shows an animator at work, with a relevant topic of conversation.
It probably does not pass the Bechdel Test. I can only think of two named "women" (does a ten year old girl count?), does conversation about an apparently male boxtroll count as "not about men"? There's no reason it couldn't have had clearly female boxtrolls, but they didn't.
Seven face-sucking leeches out of ten.
Final thought: and whatever you were promised, there are no rivers of blood.