Hey there, pena!
Both the WD My Passport and the WD Elements should work without any issues with your TV. As long as it supports NTFS-formatted drives, you shouldn't encounter any issues. If, at some point, the external fails to be recognized by the TV, then you should consider backing up the data and re-formatting it.
You can refer to this tutorial from our knowledge base about partitioning & formatting (in case you need assistance with the steps):
http://products.wdc.com/support/kb.ashx?id=ZS1kgM
Other than that, @BigBlueHouse is right. If your friends' WD My Passport was formatted for Mac OS, then you most definitely won't be able to pick it up by either the TV or the Windows computer (due to the HFS+ format).
Hope I was helpful, too. Best of luck!
SuperSoph_WD