Frankenfluffy: The Witch's Cat — Lynne Pickering

Matilda goes to a Witches' Convention
and leaves Frankenfluffy her clever mischievous
cat- home alone. He gets into mischief in the magic room when he tries his hand at magic and turns five mice into cats. They get out of control and fly around on a broom and turn Matilda's house into a shambles.
An amusing story for 8-10 years.