How get a bigger butt without doing anything?

It's difficult to get a 'big butt and big thighs' without eating certain foods, although strictly speaking you should just stop watching what you eat to achieve the results you're after -- fatty foods and junk foods will all contribute to increased fat in those areas. These foods aren't very good for you, though. Other than that, you can try going to your local gym and talking to a personal trainer or someone with experience who can tell you what machines to use and exercises to do if you want to build muscle mass instead of fat. You could try to be happy with your skinniness -- not all people are blessed with thin thighs and a small rear, and they tend to be much-envied. Having a large butt and thick thighs is not all it's cracked up to be.