The main thing I can see from this topic is that as the film makes it quite clear, his appearance is more complex, mature and appealing here because he is the main protagonist of the film, instead of a supporting character on the previous films, where I can definitely see that he does have a more basic appearance from.
I like how this media image gallery of Timon's has turned out now where you can actually see the differences in how he appears in different types of animation and film media:
http://disney.wikia.com/wiki/Timon/GallerySo of course, on this film of 1 1/2, he is going to appear more like what a Main Disney film hero should appear like: Quite appealing and more likeable in both appearance and personality. It's a habit that Disney animated film creators have had and it's very obvious that a lot of their work on this film went to Timon himself, because they had a particular interest in him and so they gave him much more depth here.
It should also be noted that some of Timon's personality traits are incomparable to the previous films and media because a good deal of his behavior on this one is uniquely different such as in dealing directly with personal conflict. Many people out there commonly see him as a "joker" and sarcastic LK character because of the first film. But 1 1/2 changes this almost altogether about him in a truly more positive light and that more people can relate to.
[spoiler][quote="Zonofon"]

[/quote]
Funny thing about this pic comparison of Timon between the third and first films is that he's actually missing the edge of his back markings on the right![/spoiler]
"I found a place that was beyond my wildest dreams. But..., it still wasn't home." - Timon; Lion King 1 1/2 (3)
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- If you were to die today, where will you spend eternity?