After viewing the clip you could invite the class to consider Ben's feelings about moving and collect these into a circle of feelings on the board.
You could then ask the children to think about Ben's feelings when he is in the park and meeting new children and add their suggestions to the circle, perhaps in a different colour or font, and reflect on the range of feelings and Fred's general mood.
You could ask: "What could Fred do that might help him feel a bit better?" You could use the opportunity for children to draw on their own experience of change - moving house, school, class, clubs.
In pairs or small groups the children could discuss or write on speech bubbles what they might say to Fred about leaving his friend Billy and making new friends.