Yes it can be done but you will have to get your hands on the APK for it to work. This is because Google Play Store does not exist for the FTV. So to get around this:
1. Get on a PC and log into your Google Play Store.
2. Find the app you want to load onto the FTV.
3. Copy the URL of the webpage of the app you want the APK for.
4. Now go to: http://apps.evozi.com/apk-downloader/
and plug that URL in.
5. Download the APK to your PC.
Now it is just a matter of pushing the APK to the FTV to install the app. That's about it. Remember, just because you can get your hands on an Android app and install it on the FTV does not mean it will work 100%. All you can really do is install it and see if it works or not.