Watch the story of Nobot the Robot with no Bottom by Sue Hendra: https://www.youtube.com/watch?v=1KaIGt4qxYM
At home perhaps you could raid your recycling bins and find some things to make your own junk model robot. Think about what junk modelling items would be best for the arms, legs, head...and yes... a bottom!
Once you have made your model can you think of some adjectives for your very own Nobot. Remember an adjective is a describing word. There are lots of adjectives you could use to describe his feelings throughout the story. How do you think he was feeling when playing at the park? How about when he first discovered he had lost his bottom? Or when his friends all offered to help? And how about when he finally found his bottom?
You could write a list of adjectives on a piece of paper, or on post it notes if you have any and stick them on your robot.