One per case. That's how this Bowser Jr. minifigure is packed in with the K'Nex Super Mario Series 4. So unless no one in your area is paying attention to these, you better get tot he fresh case first if you want him! That's what I had to do - I saw many cases over the past few months but all were missing their Bowser Jr. I found a fresh case shortly before Christmas and was able to squeeze almost every figure in the case (so you don't have to!) and I can confirm his code is 05(underlined 1)4150.
I've had Bowser since one of the earliest blind bagged waves. When I heard a Bowser Jr. was being released, I knew I'd have to get to searching! He's just too cute to pass up!
Bowser Jr. isn't as sturdy as his elder counterpart. His shell is held on with a soft rubber tab, so it falls off easily. The spikes on his shell and his ponytail are also soft rubber. If a kid plays with this guy that ponytail isn't going to last long.
Otherwise he's a great minifigure, albeit difficult to obtain.