Today only, Pogo is offering 25% Off Undiscovered World Episodes. No promo code required, the prices have already been adjusted in game.
http://www.pogo.com/games/undiscovered-world
I was able to get 11.
If you were one of the people who got a free popup badge (glitch) for Mystery Down Under each time you did a Samurai's Gold episode then be aware as those are showing the sale price too.....but you do not need to give away your gems if you already have the badges.