There's a handful of classes that are shown on the Member Levels list, but don't appear as options on the dropdown menu when selecting a class. I checked on both of my devices, using Windows (Chrome) and iOS (Safari), and a few other members have mentioned not being able to find some of these classes as well.

Here's a list of the classes from the Member Levels list that I found were missing, with their respective level (I'm at level 45, so I can't check for any that are higher than that):

• Friend (1)
• Blogger (2)
• Bumblebee (5)
• Furry (5)
• Snake (5)
• Bubble (5)
• Potato (7)
• Spud (7)
• Poultry (7)
• Onion (7)
• Knight (10)
• Dancer (10)
• Luma (13)
• Junimo (13)
• Banshee (15)
• Doodle (15)
• Enthusiast (20)
• Updooter (20)
• Redstoner (20)
• Gamer (20)
• Star (20)
• Detective (20)
• Jedi (30)
• Sith (30)
• Hobbit (35)
• Gnome (35)
• Superstar (40)

I wanna say that a lot of these are part of the group of newer ones that were added a few months ago, but I can't find the wall posts in which they were announced to confirm this.