When the little people go into the Vet's from the outside the pipe they enter is completely round on the inside but when they emerge inside there is a flat little floor board extending into the pipe.
Carl starts to file through the chain leash on the mean dog to scare Valerie into telling him where their camp is. Why? He controls the leash and would just have needed to hold it closer. There is no reason for him to file through it.
The chimp is supposedly running loose unsupervised in the veterinarian's store, but a human shadow can be seen following him after he lets the cat out of its cage.