Fat
If you eat both the moon and the sun with a spoon you'll get fat. Maybe if you only ate one you could get away with it, but you wanted both and now you're pretty fat.
Picture yourself digging your spoon into the moon, then into the sun, and gulping them both down. Watch your stomach swell with the sun and moon fats. No going back now, gotta finish.
し
あぶら
None
Once you're nice and fat, you look in the mirror to admire your new girth. But that's not you... it's a sheep (し)!
Oh nooo you've turned into a fat sheep! You're actually pretty adorable and round and fluffy, but you liked being a human!