The bald spot on Fifi's tail is only visible after he finishes his story about being "attacked" by wild animals and shows it to everyone. It is not seen before or after.
When Elliot, Giselle, Buddy, and McSquizzy get caught, Fifi brings out the shock collars which are all the same size. Once the 4 are tied up, the collars all range in size depending on who they're placed on and where.
At the end of Open Season, Elliot has lost his right (and only) antler. In Open Season 2, it's back again.
When Fifi gets out of the pool, his hair is is a straight, wet, soggy mess, but earlier when Boog splashed them all with a wave of water that sends all the dogs floating out of the back room, all the dogs are dry.