Ultra Stack Showgirls is my favorite in the Ultra Stack series! I've played a bunch of them over the years and this one, while similar, is unique with respect to the way the bonus is done!
You win in Ultra Stack Showgirls by landing winning paylines and to help, wild symbols may land on reels 2, 3, 4 and 5. The real fun, not surprisingly, is with the bonus which is triggered by landing bonus symbols on reels 2, 3 and 4 and is called the "Cabaret Feature"!
The Cabaret Feature consists of a Mini Game and then 8 Free Games. Upon trigger, you select from 9 Picks and for each Showgirl you find, that symbol is transformed wild in the bonus. Your Free Games start if you find all 5 or when you choose the "Start Free Games" symbol: if you choose well, you then have a great chance to score an awesome Big Win or Jackpot and while I didn't do that well, I had such a fun time, Enjoy!