A family and being in a new place is all strange and unfamiliar territory for Paddington. He makes a lot of mistakes and struggles to fit in with these humans, just as they don't know what to make of him. The eldest daughter, who, herself, is trying to fit in at a new school. She doesn't want this "strange" bear in their family because she thinks they are "weird" enough.
. . . because, ultimately, this film is about adoption. Just as in adoption, the family's life becomes a mixture of chaos and joy. I, like Mr. Brown, wanted my family's life to just return to "normal" after Cava's arrival. Like Paddington, Cava put our house in sixes and sevens and upset the routine of our days, but, like the Browns, our routines needed upsetting so that it could be filled with more love and joy than it had ever been before. Cava was our little brown bear who opened our family up to so many new experiences and people that we never would have had or met without him. As Mr. Brown says, "It doesn't matter if someone comes from halfway round the world, if you love them, they are family." This hit straight to my adoptive father's heart because of how true it really is. In so many ways, our family, like the Browns, have grown closer and stronger because of him being a part of us.
When he came to London, Paddington had a small note attached to him for someone to "please look after this bear" and the filmmakers clearly have. This film is absolutely delightful, warm, and full of heart, It's a treat for the whole family.