These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fridge Horror: Ralphie mocks Frog's prophecies saying "he told me I'd meet a tall dark stranger and go on a long journey. Considering what happens to him shortly thereafter....
Fridge Logic: Not that any of the characters would be likely to realize this, being animals and toys, but any canned goods company using a Droste Image as their label probably wouldn't bother to display more than four or five iterations, since after that point it would probably be too small to print in detail even if you could see it. Which makes the Child's vision at the bottom of the pond even more creepy and confusing.
When the title characters get smashed with a rock.
What Do You Mean, It's Not Symbolic?: The Mouse and his Child both yearn for some personal independence from each other and their reliance on their wind-up key to move. In fact most of their problems stem from the fact that their wind-up key stops and they need someone to turn it for them, and many animals exploit this particular weakness.
What Do You Mean, It Wasn't Made on Drugs?: There are several "trippy" segments in the film, including a section where the Child sees the label on the Dog Food tin repeat inside itself numerous times (because the mascot depicted on the label holds an exact replica).