Who are the characters, and what are they? Simon is the main character, and he's a dog. Miss Adora Belle is the character causing the problem, and she's a cat.
The theme is that sometimes you just have have to share.
We have come up with a summary for Simon's New Bed, that won't give away the ending. A dog named Simon gets a new bed. but before he can use it he goes for a walk. But, when he returns, an uninvited visitor, Miss Adora Belle, the cat, is in the middle of his new bed, sound asleep! Simon tries different ways to get her out, but only one works a little differently.