I love a bubbly character. My favorite is Simi, a young demon in Sherrilyn Kenyon's Dark Hunter series. Simi has a child-like curiosity for life, tells it like it is, and is deadly when she needs to be. She also thinks everything tastes great with barbecue sauce, including humans. I find characters like this lovable and highly entertaining. They put a smile on my face when they routinely pop up in a story. It doesn't matter to me whose side they're on. Usually, I find them to be scene stealers.
In my current WIP I have a bubbly secondary character that I'm falling in love with. I made the mistake of toning her down at first, and she ended up with as much personality as a dead fish. In the re-write I changed her back to her overly enthusiastic, talking a mile a minute self and she's stealing the show. I'm considering telling her story in another manuscript.
Characters like these are sometimes the secondary characters, but they are as important as the hero and heroine. They create balance and sometimes, comic relief. If I read about a hot headed hero, his laid back best friend helps even him out. But be careful. Sometimes you may find your secondary character out shines the hero/heroine.
What about you? What kind of characters do you like? Do you have a favorite? What makes them special?