A young, small and scrawny raccoon waits on the riverbank for Milo to catch a fish with his tail. When Milo catches the fish and drags it ashore, the raccoon is suddenly a full-sized adult, clearly twice the size of the raccoon in the previous shot.
At the beginning of the film, Milo is seen as a very young kitten, perhaps three weeks old, nursing from his mother. After Milo falls out of the hayloft and immediately meets Otis for the first time, Milo appears to have aged at least a month. (This only applies to the English-language version; in the original Japanese version, the first meeting between Milo and Otis does not occur until about 6 minutes after the hayloft scene.)
When the bear is splashing in the river, he decides to get out and head for the shack where Milo is hiding. The soaking wet bear is suddenly seen dry as he tries to open the door of the shack.
When Otis treads through the mud of the Deadwood Swamp, looking for Milo, his paws and legs are dirty, in the next shot, they are clean.
When the bear is in the river, he sees Milo float by in the wooden box. In the next scene, the bear is somehow again downstream of the box that just floated past him.
When Otis is distracting the bear from Milo's floating box, you can hear a human voice shout out right before Otis runs back towards the trees to lead the bear away.
When Otis is just near the shore after having escaped from the rock in the ocean, the device used to pull him onto shore is visible in the breaking waves for a brief moment.