At first I thought the whole concept was confusing. I watched several videos of Morning Musume in different TV-shows and the members were never the same. It took forever for me to memorize the members. The whole concept of old members graduating and new ones being added was confusing, but exciting cause it was so new to me. Watching old shows, old music videos and reading up on the history of the group I soon came to have my favourite members, and interestingly enough several of them had already graduated by the time I discovered the group. In 2008, the group's producer (Tsunku) came up with the idea to not hold auditions for new members for a while (previously new members had been added pretty much each year) to let the fans have a chance to get to know the present members even better. This meant that MoMusu had members from the 5th through 8th generations all the way until early 2011, when the 9th generation was finally added and it was a big commotion. The 9th generation got lots of promotion and I got to know them really quick. 10th generation was added later that same year and I've just gotten used to them. The first single with the recently added 12th generation is yet to be released. After the members have graduated they all go on to either do solos or to form other groups. A big group has been formed with several of the graduated members called Dream Morning Musume (and it really is a dream to see them together).
Another thing that I like about them is that not two songs sound alike. This video shows how much their sound has changed since they began and how they sounded in early 2011. But since every song is different there's no guarantee what the next one will sound like. Lately their songs have been inspired by dubstep for example.
MoMusu has been going on since 1997 and is still going strong. Out of Morning Musume grew Hello! Project an agency that came to host several groups and, up until 2009, several of the graduated members. In March 2009 the older members graduated in a huge concert (which is still my favourite of all time). I still can't watch the end of this concert without crying, cause it's so lovely how they all thank the crowd and eachother and how they all are teary or crying at the end of this song... Which is the way it is every time a member graduates.
So that's it. I love the concept, I love the personalities of the members, I love how their style changes and how every song is different but almost always great anyways.