Here's a list of all the ranks we have we do still have more on their way

1. Chao obtained once joined

2. Goomba obtained at 20 posts

3. Flicky obtained at 50 posts

4. Bullet bill obtained at 120 posts

5. Bandik botained at 220 posts

6. Hammer Bro obtained at 350 posts

7. Squirrel obtained at 500 posts

8. Dry Bones obtainted at 700 posts

9. Cat obtained at 1000 posts

10. Toad obtained at 1250 posts

11. Armadillo obtained at 1550 posts

12. Koopling obtained at 2000 posts

Plus, there are more ranks. You'll have to find out what they are.