Helena Bonham Carter says playing a witch was a ''dream come true''.The 46-year-old actress - who has children Billy, eight, and Nell, four, with partner Tim Burton - admits one of her career highlights was portraying evil Bellatrix Lestrange in the 'Harry Potter' movie series, though her kids don't understand why she always plays dark characters. She said: ''That was my dream come true, playing a witch. My daughter asks me, 'Why do you always play baddies mama?''' Playing the role made Helena known to many young girls and she thinks she sets a good example - because she enjoys her food. She said: ''Am I a good example? Well, at least I'm not too thin. I eat.'' The actress is also a source of advice for her young 'Harry Potter' co-stars, recently advising Daniel Radcliffe during a discussion for Interview magazine, though he isn't the only star to come to her for help. She said: ''I've had lots of conversations with Emma Watson too. She is very, very bright.''