you can save a downloaded YouTube videos to your SD card and play them using third party apps.
To download YouTube videos, you can try Gihosoft TubeGet, a free and easy-to-use video downloader, you just need 3 steps to complete the download process.
Then you just need to connect to your mobile device and transfer the videos to your SD card or inner space to play them.
If you are using Android smartphone, TubeMate can be your good helper, it’s a very popular Android app in market for downloading YouTube video.
If you have any suggestions let me know...