Well, I'm sure it's old but...
I'll leave you to figure out why. The joke never gets old, even though it's groan worthy.
For extra thematic points, they were all picked in order, using the im@s OfA stat sheets. Azusa was first, and Chihaya was last.
Any reason for it? Not really. I just thought that some bad jokes are good for a second time around.
I was tempted to call my idol group Slender, except Chihaya was overpowered in im@s2, so I decided against it.