Here are some ideas for names that are fun and playful, without being offensive:
Based on size and fluffiness:
* Chonk
* Fluffy
* Big Boy/Big Girl
* Tubby
* Plumpkin
* Sir/Madam Snugglebottom
* Butterball
* Pudding
* Marshmallow
* Muffin
Based on personality:
* Grumbles
* Sleepy
* Snuggles
* Cuddles
* Mr./Miss. Personality
* Boss
* King/Queen
* Captain
* Sir/Madam Pounce-a-lot
Funny/Unique:
* Sir/Madam Meow-ton
* The Great Meowdini
* The Fluffy Overlord
* Chonkzilla
* Captain Chunk
* The Purrfect Storm
Ultimately, the best name is one that you and your cat love. Consider what makes your cat unique and choose a name that fits!