Chosen Solution

I have two sets of these interactive figures that either do not move or sing or sing but do not move. How can I repair them?.

Maybe finding a year on these toys, a manufacturer, or uploading a picture of them would help. I’m assuming you have the 2002 models: https://youtu.be/dsQJFJLA2q0 It may be that the batteries are in wrong, or the battery terminals are corroded and needs to be cleaned. Try leaving new batteries in the toy for a while, it may take time for the batteries to warm up and the toy to start working. For the speaker not working it could be that the wires could have come unsoldered. Try moving the two toys, not forcing it, but the gears could be stuck, or the motor that starts up the toy could be weak/stuck. If you here any grinding turn it off the motor is burning out, and needs to be replaced.