None of the human characters are surprised to hear the chickens talk.
At 0:28:25 -the unfinished edges of the corrugated cardboard can be seen. However this is on a model of Fun Land Farm made by the chickens, so is deliberate.
From 0:58:55 -the collars continue to work without being powered.
Despite the fact that it is evident that the chicken farm is visible from Ginger's island, the chickens aren't aware of the farm's existence until they are forced to infiltrate it.
Despite being remarried, Melisha still goes by the name 'Mrs Tweedy'. As made clear in the first film, this is her married name that she got off of her previous husband as opposed to being a maiden name.