I'm not sure why but Helen Oxenbury books are always a big hit with my daughter. My mum loves them and read them to me when I was a baby, so they have withstood the test of time!
This is a fairly big book with good clear drawings and simple lyrics that flow well. It is a very short book, but my daughter adores it and you can't ask more than that! At 18 months she is switching more to simple stories, but this is definately one I will hold onto for any future children.