The irony here is the music they're lipsyncing to isn't even theirs. On the original recording, Roger McGuinn is the only band mamber playing. Everyone else is a member of the original Wrecking Crew. (Hal Blaine, for example played drums) The only reason McGuinn was included in the original recording was because nobody else could do the sitar -like sounds he could get.

Of course, that kinda thing went on in the recordings of nearly every group of the day.