I had the same issue on my game. It's actually caused by poor programming in the last world that happens no matter which character you beat it with first. Since you switch between characters without a proper drop, the portals still think that you are playing with the character you dropped with. There are two ways to fix it. 
  
1) Perform two drops without interacting with ANY portals, special or otherwise. This means if you have already interacted with at least one portal in your current character session, you will have to drop three times. I have noticed that this tends to switch the portals back to their correct characters. 
  
2) Beat the game again. This will essentially cause you to activate the glitch again, which will cause the portals to switch again. This method has worked for some, but not for others. If you attempt this method it may take two or more attempts to work correctly. 
  
Hope this works.