So as the title says, windows phone 8 apps Where's My Water and Where's My Prerry are both free!
I think it's only 24 hours.
I'm pretty sure it's only for windows phone 8 devices as well.
I've only played Where's My Water on the iPhone and it was a fun game.
http://www.windowsphone.com/en-au/store/app/where-my-water/1…
http://www.windowsphone.com/en-au/store/app/where-my-perry/7…
Looks like you might be able to also download the games and install them manually if you don't have a WP8 device just yet.
On both of those pages down the bottom left there is a download manually link. This will let you download the .xap files (31mb for perry and 39mb water). You can then move them over at a later date and install them.
True ozbargin style really. Maximising the free-ness…