Whimsical and Playful:
* The Muggle Wump and the Magical Mishap
* The Muggle Wump's Big Adventure
* The Day the Muggle Wump Took Over
* The Secret Life of the Muggle Wump
* The Muggle Wump Who Couldn't Be Tamed
Mysterious and Intriguing:
* The Mystery of the Muggle Wump
* The Curious Case of the Muggle Wump
* The Last Muggle Wump
* The Muggle Wump's Legacy
Funny and Outlandish:
* The Muggle Wump Who Ate the Moon
* The Muggle Wump's Hairy Tales
* The Muggle Wump and the Talking Toilets
* The Muggle Wump's Guide to Mayhem
Bonus:
* The Muggle Wump of Wormwood Scrubbs (evoking "Matilda")
Ultimately, the best title will depend on the specific tone and plot of the story. Consider what makes your Muggle Wump unique and what you want the reader to feel when they see the title.