McTube Pro, a YouTube client, used to be able to save YT videos for later viewing. But the last update removed the feature, reputedly at the "request" of Apple. One presumes YouTube didn't like folks watching a video without seeing their ads, and leaned on Apple.
You can still save them using any of several Firefox extensions on your Mac or PC, then transferring them to your iPad for watching. However, if they're only available as Flash movies, you'll need Handbrake to convert them to a format the iPad can use, perhaps mp4, and that will result in a quality loss.
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