How to switch the type of special orb?

Ren_Hao

When I defeated the level 500th, I got a new type of special orb and assistant will be changed to Wilbur, then I went back to previous levels in order to complete 3 stars achievement, I found the type of special orb and assistant was changed to Nero, and even I can not use Wilbur's type after level 501st. I want to know how to switch the type？ 

Jelly_Jenny

Wilbur turns into a good boy after level 500 which means he can be the assistant.  However Stella and Nero are keeping an eye on him which means that Nero will take turns every now and then.

You'll have Wilbur as your assistant occasionally but they rotate with Nero. In short you might have either one on any level after 500. 

Have a Bubblific day!