Continuity mistake: When Dennis first meets the man who cut his own foot off, it's because he shoved his hand (with a cup in it) right in front of his face. When the shot changes so we can look down at who it was, we see that his hand is nowhere near Dennis' face (he would have had to have been standing up and leaning over to reach his face, when we see him he's sitting down and leaning back against a wall).
Add timeGary O'Reilly
Continuity mistake: The peasant with the rock is killed by the Jabberwock. When his skeleton first lands next the Dennis, it has a bit of flesh left on it but lots of bone is visible. The shot then changes to show Dennis backing away and the peasant's corpse now has a lot more flesh on it and the legs are in a different position.
Continuity mistake: Just before Dennis rescues the Fishfinger family, the knight is riding the horse that the Dog knight was riding earlier. When the Knight and Dennis are walking through the destroyed village the knight is riding a different horse. The pattern of white on its nose is very different.