So,
Option A:
1000 Rainbow Star
2000 Rainbow SuperStar
3000 Rainbow MegaStar
4000 Rainbow AllStar
5000 Rainbow Spirit Chaser
6000 Rainbow Spirit Seeker
7000 Rainbow Spirit Keeper
8000 Rainbow Spirit Wizard
9000 Rainbow Spirit Master
10000 Ruler of the Rainbows
15000 At the End of the Rainbow
20000 Over the Rainbow
50000 Has no life!

or
Option B (fewer steps, larger spans, no Rainbow Spirits):
1000 Rainbow Star
2500 Rainbow SuperStar
5000 Rainbow MegaStar
7500 Rainbow AllStar
10000 Rainbow Diamond
25000 At the End of the Rainbow
50000 Over the Rainbow
100000 Way too much time on their hands!

or
Option C:
2250 1 Qookie
2500 2 Qookies
...
3000 1 Peegue
3250 2 Peegues
...
4000 1 Loof
4250 2 Loofs
....
5000 1 Stinky
5250 2 Stinkys
etc.