Question: I Remember that I could play with any character in the Head Cup. Why I can't?
Answer: That one was a useful glitch (a mistake of the game) that was Fixed in the 3.4 Update, but you can still do it. When you are on that scree, go to the Upgrades Screen or Costumes Screen and go back to Head Cup. You will be able to swipe it. In each update, the developer corrects some mistakes, but here it wasn't very good fixed. If you want more information about Glitches, a link below: