To make it happier, don't let it faint in battle, battle with it often, heal it often. If you Pokemon seems tired, then give it a healing item to make it happier. The great thing about Soul Silver and Heart Gold it that it's very easy to tell how your Pokemon is feeling by talking to it! For example, Sudoowoodo does NOT appreciate being in the water, and it'll tell you that. Other ways to make them happier are to give them Vitamins and Rare Candys. Don't give it Herbal Medicine or other things it doesn't like, like a berry that has a flavor it hates.
I honestly have no idea what you mean by "cuter".
Edit Ok, occordding to your chat posts, apparently you figured out that it would be cuter if you gave it hair cuts in the game..I'm still kinda confused by this whole thing.