Where's My Valentine?, a free game co-starring the protagonists from the Where's My series, is available for free on iOS and Android.
The game includes 12 Valentine's Day-themed levels, starring Swampy, the shower-loving alligator from Where's My Water? and Agent P, better known as Perry the platypus from Phineas and Ferb and Where's My Perry? Each character gets his own set of levels, which showcase the water-based gameplay from the co- protagonists' own apps.
You can download the free app from the iOS App Store or Google Play. If you like what you see, you can unlock more by purchasing Where's My Water? or Where's My Perry? for $0.99 each, both of which are available from links within the app.