On the left is an interpretation of my weasel character's original design, and on the right is how I tend to draw him these days. He used to be a bit bigger and more menacing, with unkempt fur and a perma-smile. Over the years he got smaller, cuter, and fluffier, to the point where he occasionally appears to be more of a squirrel than a weasel.

The personality and backstory changed, too. Classic Weasel was talkative and was employed as the mascot of a fictional insurance company, marketed on the theory that humans might be more likely to buy from a fellow mammal than from, say, a duck or a gecko. Modern Weasel is more of a silent protagonist, with a "Velveteen Rabbit"-style origin -- a children's toy turned into a real animal by magic.

At this point they're basically entirely different characters, sharing only a species, fur pattern, and lack of actual name.