Could we seriously post it as a note or something somewhere what OG means? xD
OG means "Old Girl" and refers to someone who has graduated from [whatever], in this case Morning Musume. ANYONE who has graduated from the group is a MM OG. ANYONE who has graduated from H!P is a H!P OG. ANYONE who has graduated from Harvard University is a OG of Harvard University... Or OB (Old Boy) if the person happens to be male.
It's wasei-eigo, I'm pretty sure. That's what the meaning is, and when Reina graduates she'll be an OG of MM and H!P. Has nothing to do with age whatsoever, it's pretty much just "Old member" anyway. Now why don't they just do that instead? Because it's a Japanese term used in Japanese society, and you don't go "I'm an old member of that school/company/club" but you simply refer to yourself as an Old Girl/Boy. Not a big deal, really.
JunJun's gotten really cute lately. I kind of want her to come back and just be under UF as a model. She's certainly tall enough, and doesn't seem to be doing much at the moment.