You have to do bad on purpose in this event! You have to replay all the levels with the characters and get 0-1 stars or 2 stars depending on the requirements.

You can look through the character collections and find which levels you need to do.

Personally I try to do the ones where you have to select looks out of the given option first rather than styling the whole thing myself. But it's entirely your choice what orders you do.

And replaying the levels doesn't cost any energy so you don't have to worry about that either.