In the original movie Stitch was much better. He was not just a "prankster out for a good time". He was a - quite frankly - disturbed character, made that way by his creator. His anti-social tendencies were overcome by the friendship of Lilo who herself had trouble fitting into society. Together they were able to help each other grow and change. Now that at least is character development - with an overdone and re-hashed plot, granted, but still character development. (They could have gone much farther with his creator making him bad, the whole nature vs. nuture theme, is the capacity for evil inherent in people or is it learned, and if his creator is viewed as "god" and his redemer is Lilo, then what does that speak to about modern religion - however it is a kids movie, and I see why they did not want to go there). Since that time Stitch has just become a vehicle for fart jokes and and actions that if quite frankly my kids did, there would be some serious parenting repercussions.
-dave