Google is continuing with this free app of the week promotion, but it's still just for family-friendly kids apps. The third selection is now live and it's a $5 app called Thomas’s Musical Day for Percy. Now it costs you nothing to subject your children to the horror of anthropomorphized trains that misuse apostrophes.
This is, of course, a Thomas the Tank Engine app with stories, song, and other content. The app is fairly new with only a few hundred downloads. I assume that's about to shoot upward now that the $5 price is down to free.
You can only get the app at no cost by going through the family section of the Play Store and clicking on the free app banner. Alternatively, you can use this link that takes you to the same place. Enjoy... maybe. I always found Thomas the Tank Engine to be mildly disturbing for some reason.