A popular Japanese pop
group, consisting of about a dozen cute teenage girls. Think Britney Spears
in numbers, without the tit craze.
A friend of mine reports a very good description of them, delivered by a Japanese girl about to perform one of their songs at a festival in Germany:
Morning Musume is a group of... <looks at her friends with a questioning expression, gets no response> ...a group of girls, and there's always some members leaving and new ones coming, so nobody really knows how many there are right now, or what their names are.