Quackpond is a one-trick pony of a game but it is a handsome pony with a good trick. I am not sure how much effect you have on the plot but the story plays out in a very interesting way with the fun being working out what is going on.
The idea probably wouldn't work for a larger game but Quackpond is nice and short. It was fun playing with my duck and when it was over I found that I missed Brown Boy the Mallard.
(Spoiler - click to show)Quackpond implements a really neat storytelling device - it purports to be a slightly janky old fashioned web-game involving feeding ducks but as you play the (very simple game) a drama is playing out in the forums. This is a fantastic idea for a story and the writing is appropriately forum-like but I felt that more could be done with the idea. Still, what we have is really interesting and worthwhile the 15 minutes or so it takes to play.